Blue tits

Depends on the environment of the area, but as you live in a flat, I'm guessing it's inevitable they'd move away as soon as fledging. They rely on cover in the early days as they can be easily picked off by corvids, gulls, cats etc.

Thanks for the reply. Ok that makes sense we only have a few large trees but no hedge like cover hopefully they all made it down to the woods half a mile down the road i have had a good look around on the ground below and i cant see any of them so hopefully all made it successfully because of the cats around thats been my biggest worry for them all along. So the wont return to there actual nest now they have left it the once? Thanks again 

Tom 

Blue Tits usually only have one brood per year, very rarely a second attempt maybe if they've lost the first brood ...  your fledglings made it to cover where their parents can continue to feed them for a while!