Anyone able to tell me what bird this is?

Hi Jilly,     the bird is a little Goldcrest,   was it in a collision with window or structure ? 

Thank you. It hit a glass wall

Assuming it is just stunned and not seriously injured, just leave it in a safe quiet place outside and hopefully it will recover and fly off in time.   I've rescued a couple of Goldcrest which were just stunned after hitting windows and placed them in the top of a planter pot protected from predators and thankfully each one flew off;  first took about 30 mins but the other took over an hour to recover.    Fingers crossed this little bird will recover too.   Good luck.