Miles - Nature

I heard talk today of a survey of a (fly?) or other biting insect
which is supposed to be rare, which occurs, sometimes in
discomforting numbers, in the estuary of the Dee?

Anyone heard of what the insect is, and point to some text
for a description?
2 people I know were bitten several times, although as far as
I can tell the reactions were mild.

I had assumed it was a mosquito.
Miles