Sacha wrote:
All these were new in the pond this year - just shows how warm it's been and
how ideal the conditions for these plants. I don't know their botanical
names but to us they are water cabbage ....

Usually called 'Water lettuce' - Pistia stratiotes, although it is a
member of the arum family with tiny greenish, arum-like flowers tucked
between the leaves. It's a very nice thing when growing well although
it can be temporarily invasive. I used to overwinter it in shallow
tubs of mud at around 10C.

.... water hyacinth

Ah the dreaded Eichornia crassipes! Fabulous flowers, but it's a
formidable and worrying pest in tropical regions. It has taken over
entire lakes in Africa where there are few predatory pests to keep it
in check. In its native Amazon basin home it never causes problems,
but when introduced to similar climates elsewhere, Eichornia is a
major scourge blocking out light to the water and causing submerged
water plants to die out, resulting in de-oxygenation of the water and
fish deaths. Growth rates are truly phenomenal, waterways can be
rendered unnavigable by the dense, metre thick carpets of herbage and
the plant is not easily controlled by conventional means.

Not a problem here though - the first hint of cold weather will slow
this and Pistia right down and a couple of frosty night will kill the
plants completely.

.... water forget-me-not

Isn't this Myosotis scorpioides (formerly palustris) ? It's a pretty,
waterside native perennial that should overwinter perfectly well in
any part of the British Isles.