Thanks guys.
Guess what, I put it back in the nesting box and today it is on the floor again. Obviously thats where it wants to be! It is totally feathered and appears to be feeding itself, although I think the dad is still feeding it as well. I'll just keep an eye on it. I don't think any other birds have pushed it out as the mum and dad are still pretty protective. Unless of course one of the other babies has pushed it out as they are all poking their heads out and one other baby is almost coming out half way.
It still doesn't seem to be able to fly but I'm sure it will soon.
Thanks again.