I'm in Preston, North West of England.
The fishes seem to be fully grown whenever I see them, at around 2 inches long - though I coould be wrong.
They move very very quickly through the water and are found around rocks or stones in shallow ponds, and in the weeds - and always seem to be close to the edge.
Seem to be gregarious.
I have seen them at the edge of canals too.
Here is a photo (sorry - had to catch it in a net just to get an image of one them!)
