Is it possible for mosquitoes or bugs to breed in a boiler? We have a whole load of them in our house?

We have a lot of flying bugs- they are small, with little wings and look like a miz of a mosquito/ small black fly- like a fruit fly. They bite me every night when I'm asleep and it's driving me crazy. We also have a sink in our room, 2 skylights and an ensuite bathroom- the only other possible sources I can think of. Any other ideas where these flying bugs may be coming from, particularly given that it's winter in London? Please help.