Baby Blue Tit advice (babies might be stuck - one meter down in hollow metal fence post)

Hi, 

I'm really hoping somebody can help..

I've just noticed some baby blue tits nesting in a metal hollow fence post (they are roughly one meter down, maybe more)

I'm worried the little birds will be stuck when they come to leave the nest..

Will they be able to fly up and out of the fence post or should we intervene? (the diameter is roughly 10-15cm squared) 

Any help much appreciated, worried sick about them :(

Thank you

Zoe