I took some photographs at Brown Moss in Shropshire earlier this month, so trying them on the Western Europe dataset.
Rumex acetosella - correctly identified
Rumex maritimus - correctly identified.
unidentified thread-leaved plant, probably a capillary-leaved crowfoot, but I thought that these were subaqueous - misidentified as Myriophyllum aquaticum, but the second alternative of Ranunculus trichophyllum could well be correct.
suspected Persicaria laxa - identified with high confidence as Persicaria maculosa (wrong), with Persicaria hydropiper (also wrong - I used the taste test for confirmation) in second place. Persicaria minor, which I haven't excluded yet, came in 5th. (At least it didn't focus on the Crassula helmsii dominating the photographs.)
dwarf St. John's Wort, perhaps depauperate Hypericum perforatum - offered Hypericum tetrapterum, Hypericum humifusum and Hypericum perforatum, in that order.
suspected Veronica scutellata, but I have to check the books to make sure it's not V. catenata or V. anagallis-aquatica - it agrees with me
Lythrum portula - misidentified as Portulaca oleracea, with the correct identification as the second choice.
laminar-leaved crowfoot - identified as Ranunculus peltatus, so it at least it's in the right area.
and from Prees Heath
Trifolium arvense - correctly identified
Clinopodium vulgare - it agrees with me
tatty likely Hirschfeldia incana - got it right, but confused me by giving the botanical name Erucastrum incanum and the vernacular name Greek mustard.