A midge or gnat overwintering in Combe Bank caves. Now identified as a mosquito - thanks!
No interactions present.
It looks like Culiseta annulata.
I agree that this is most likely to be Culiseta annulata, which is a mosquito. There is an outside chance that it could be the very similar Culiseta subochrea, which I've never seen, but to form an opinion on that we'd need to have a clear view of the abdomen.
Assuming it is annulata, the species can breed in a wide range of natural and artificial water bodies. This is a female (relatively short hairs on antennae) and therefore capable of biting!
Entomologist and biological recorder
I will warn the regular bat surveyors!
Lat/Lng: 51.280343333333, 0.118645
OS grid ref: TQ478555