This has quite a few names but Pustula tragopogonis seems to be the latest one. I know it as Albugo tragopogonis but had just begin to call it Pustula obtusata. Never mind, Taxonomists know best. I do not like the common name here as this is really not on sunflower but Common Groundsel (Senecio vulgaris)

The first picture shows it sharing with Puccinia lagenophorae on the same leaf, with Pustula underneath, the other on top.
It is so like Albugo lepigoni - https://www.inaturalist.org/observations/57742403

A common mildew and found more often on the leaves of Plantago major and similar broadleaved Plantago species.

Here, it is shown on Plantago maritima as a white powdery coating.
In this case the plant is shared by Golovinomyces sordidus which produces the small pustules seen in Pictures 10 & 11
BOTH occurring on the same plant in this location - picture 12
Picture 13 shows typical spore-chain of powdery mildew (on Filipendula ulmaria - Meadowsweet)

Golovinomyces sordidus
https://bladmineerders.nl/parasites/fungi/ascomycota/pezizomycotina/leotiomycetes/erysiphales/erysiphaceae/golovinomyces/golovinomyces-sordidus/
and
https://www.naturespot.org.uk/node/122990

Podosphaera plantaginis
http://www.bioref.lastdragon.org/Erysiphales/Podosphaera_plantaginis.html

A small, almost invisible organism.
An obligate parasite of Spergularia (Sea Spurrey), causing ‘white rust’ or ‘white blister’.
Sporangiophores appear on the host's stem, causing it to swell and burst. The white powdery spores are then dispersed by wind and rain.

The EGGS of this rarely recorded Ichneumonidae.
It is a known behaviour of this species, which is a specialist in parasitizing Puss Moth (Cerura vinula) larvae.
These appear to be mites but have no legs or visible mouthparts and are very glossy.
By good fortune they are described here
https://www.amentsoc.org/publications/bulletin/articles/observations-of-netelia-vinulae.html
.
EDIT 2021
Added three photos


An unexpected encounter with a huge swathe of the Sand Binder. Areas of tightly compacted sand, with eroded edges and bald areas. No doubt about identity but difficult to prove without more pigmentation - picture 8
What is remarkable is that the sand, where bound by the fine algal strands, was very difficult to dislodge, requiring gnarly fingers or, better, a penknife.
This is a Winter seaweed - a gorgeous red when in full bloom - picture 9
Picture 6 shows Cladostephus fronds

Atriplex is common in Europe and the pale edge-rolls seen on the leaves are easily IDd as H.atriplicis. But for completeness one should always look for and photograph the Aphid, which is usually found inside the pseudogall.
.
Hayhurstia atriplicis is actually an aphid. We infer that the pale leaf-roll found on several species of Atriplex, is caused by the aphid's attention to the under-surface of the leaf of Atriplex.
It is a sound assumption IF you can discard three other organisms, two diptera and one fungus.
Their effects on the leaf are quite different, so it's a fairly easy call.

The pseudo-gall itself is very distinctive, pale, swollen, tightly inrolled (curled) and distorted. It is important to look for the Aphid, and photograph it for 'final' evidence.

The Aphid - https://bugguide.net/node/view/480464
The gall - https://www.naturespot.org.uk/species/hayhurstia-atriplicis
Some science - https://influentialpoints.com/Gallery/Hayhurstia_atriplicis_chenopodium_aphid.htm

Hayhurstia atriplicis is actually an aphid. We infer that the pale leaf-roll found on several species of Atriplex, is caused by the aphid's attention to the under-surface of the leaf of Atriplex.
It is a sound assumption IF you can discard three other organisms, two diptera and one fungus - Picture 7. Their effects on the leaf are quite different, so it's a fairly easy call.
The pseudo-gall itself is very distinctive, pale, swollen, tightly inrolled (curled) and distorted. It is important to look for the Aphid, and photograph it for 'final' evidence.

The Aphid - https://bugguide.net/node/view/480464
The gall - https://www.naturespot.org.uk/species/hayhurstia-atriplicis
Some science - https://influentialpoints.com/Gallery/Hayhurstia_atriplicis_chenopodium_aphid.htm

One of three - two Locations
https://www.inaturalist.org/observations/36022955
https://www.inaturalist.org/observations/35927209
My third Observation
It is widespread at this new location.

I do not find micrography easy but in this case the most obvious features appear in all Online Publications.
Typically here https://www.researchgate.net/figure/Zygogonium-ericetorum-Habitat-a-macroscopic-appearance-b-and-d-and-photomicrographs_fig1_257994888
and
https://www.semanticscholar.org/paper/The-green-alga-Zygogonium-ericetorum-Charophyta)-Herburger-Remias/5287c242f2989a0f5d25afa61aebb34a4fe64c96/figure/3

Filament type B1 in pictures 7 & 8 is quite different to the main ones and yet seems to be present in all samples - it is VERY distinctive
My cell-phone app is used for under-lighting (light table App)
I used this key successfully
https://www.algalweb.net/search4.htm
I am very grateful to @roman_romanov for the original ID.

My second Zygogonium ericetorum in as many days.
These pictures are taken 14 days later than for the previous record and I expected a much greener result - it was colder and wetter. But the samples still show the ferrous tone that is indicative of species-form.
It is widespread on the headland.
I do not find micrography easy but in this case the most obvious features appear in all Online Publications.
I am mystified by the filament in picture 14
My cell-phone app is used for under-lighting - Picture 13
I am very grateful to @roman_romanov for the initial ID.

Some online links
https://d3i71xaburhd42.cloudfront.net/5287c242f2989a0f5d25afa61aebb34a4fe64c96/6-Figure2-1.png From -https://pdfs.semanticscholar.org/5287/c242f2989a0f5d25afa61aebb34a4fe64c96.pdf?_ga=2.20015160.1429334316.1574614158-141978553.1574287727
and
https://www.researchgate.net/figure/Zygogonium-ericetorum-Habitat-a-macroscopic-appearance-b-and-d-and-photomicrographs_fig1_257994888

The UK's most northerly Walnut tree is in my garden. It is only 9 feet high and bears no fruit. It was grown from seed collected from Oxfordshire in 2001. The leaves a distinguishable as are the scars on its spindly stem.
There are only a few (maybe 8) of these north of this in the whole World. The most northerly is here https://www.gbif.org/occurrence/2408954874

On Atriplex species leaves
Usually circular blotch with distinct black pycnidia.
Not rare but massively under-recorded.

see https://bladmineerders.nl/parasites/fungi/ascomycota/pezizomycotina/dothideomycetes/pleosporales/ascochyta/ascochyta-caulina/

I have visited 10 distilleries where this fungus is rampant. Usually expresses as sooty staining on external walls, nearby trees, signposts and street furniture. It forms on structures up to 600 metres (downwind?) away from Distilleries and Bond Warehouses. It is known to cause unsightly staining on nearby modern dwellings.
It is granular and can be scraped from the surface and cultivated. Here we see examples on structures at the Blair Athol Distillery, as well as one or two from other locations..
3 Pictures showing the distinctive spore chains
https://en.wikipedia.org/wiki/Baudoinia_compniacensis

The most telling quick ID feature is shown in picture 3, they fit to form a near circle.
But, as always, we need to rely on the inside architecture for a perfect ID, thought it is sometimes difficult to photograph the features and NOT always conclusive.
It is worth looking closely at the upper and lower surfaces of hinge left-valve laterals and inner surfaces of right-valve lateral - they are serrated, worth seeking out, satisfying to observe. Pictures 9 & 10.
This is a broadly triangular, very robust and common shell.

This is not always deep red. It matures and propagates in January and is quite red from October..
During the summers, it loses pigment and growth but the fine, binding, filaments still hold the sand together.
It is not so easily seen and what 'turf' shows, is the same colour as the sand. One needs to collect a small portion (not easy) and examine through a x10 glass to see the compacted sand grains holding the filaments tightly.
Quite widespread.

A third, perhaps final, Observation of Sea Felt from me. This from a new location and giving the opportunity to again suggest that good pictures showing the overall morphology, of a light brown 'cloud' matted on the shore and probably attached to fucus species, is almost as good as detailed micro-pictures. I believe this can be identified in the field if one is careful to avoid any fine seaweed that has visually discernible filaments. The filaments of Sea Felt cannot easily be seen by naked eye.
Picture 4 shows a typical form of Sea Felt, there seems to be a central stem but this a feature of the fine threads coalescing into a bulky cord. Slip a hand under it and the threads themselves will not be discernible.
Pictures 5 and 6 contain no Sea Felt.
With a good x10 glass one can resolve the filament cords, where twining has occurred - picture 8. Picture 9 shows how fine the filaments are.
See also https://www.inaturalist.org/observations/26565760
and
https://www.inaturalist.org/observations/26669986

Sea Felt may best be identified from its overall morphology. It appears most often as a brown cloud attached to Fucus but can occur washed in unattached.
It is incredibly fine close-to and cannot be identified with just close up photos. It is JUST possible to see, via a x10 glass, the woven filaments which appear to make very fine 'ropes' - if you can see those, then you're on a good bet - Picture 11. Beyond that you will have to spend quite a time at the microscope to get photos of the minute features that ID it positively - the general cell structure and the specific presence of intercalary sporangia, mid-length of those microscopic filaments will thus conform the ID - Picture 12.
In short BOTH views are normally required for ID, one general view of its overall morphology and one of the 'rope' structure or the mid-filament reproductive cells.

See http://www.outerhebridesalgae.uk/marine/marine-species.php?id=40
and
http://www.seaweedsofalaska.com/species.asp?SeaweedID=49

Pylaiella littoralis is a brown 'cloud' epiphyte on Fucus seaweeds, I've seen it on F.serratus (its preferred host), F.vesiculosus and Ascophyllum nodosum but it may be found on others. Indeed it is often found apparently free-growing.
One needs a good glass (x10 is just OK) to ID this, as the spirally woven threads are almost unique to this. But to be certain Microscopy is needed.
See then, http://www.outerhebridesalgae.uk/marine/marine-species.php?id=40

The Red Wasp tends to look like any wasp until you spot the overall 'redness' or the reddish spots. But they can only be confirmed by facial recognition - the iNat. AI ID system here isn't up to that. yet!
Visited yesterday by the Tree Wasp and the Red Wasp in the same hour. They are not common here.
See http://www.eakringbirds.com/eakringbirds2/insectswaspsidentification.htm?fbclid=IwAR3piG2ngoUIp3Aowpoopql2AunR1juf0XaRkgWKQT8LsJnsf0YOHu558NU