loads of flies must have just hatched,how do I get rid of them

[brimfull]

when I opened ds's window this morning I could see them in the bit that you can't see when the window is closed iykwim.
I think they are young as they weren't moving much.There are loads,so shut window quickly to stop any coming in.
Gross gross gross.
Can't get them from outside as it's upstairs and I don't think it's accessible when window shut anywya.
Disgusting ,any ideas.

if they are outside then just leave them alone and soon they will disperce and fly away

no I think they are trapped in the grooves of the window.If I leave it open they'll fly in to the house.

Need a fly spray I think.