Birds nest and newborn baby - please help!

Hoping someone a bit more knowledgable than me can offer some advice please.
I live in a georgian house that has a small decorative grate above the sitting room window that acts as ventilation for the house i think.
Anyway, one of the covers of the grate is gone and a family of birds have made it their home. It's a tiny little opening so the birds can't be very big but there are plenty of them and I think have probably had some little ones in the 3 months they've been there.

Initially I was happy to have them and appreciate that we should be helping birds out where we can. But I now have a new born and the noise from the birds is constant and they sometimes seem to have a bit of a scrap and lots of fluttering of wings and drama along with the constant whistling. It pretty much feels like they are in the living room with us because of the design of the grate and it's getting bloody annoying - I mean non-stop. It's like having 5 budgies in the corner of the room.

Can anyone help me understand:
how long I can expect them to be there? (It's july now)
If there is a bit of risk of bugs and germs from them (as I say, they are not fully sealed off from the sitting room)
If i were to try and get rid of them (and I'd prefer not to) what would be a responsible way to do it?

Any help at all would be great.
Cheers