It eventually depends on the aircraft you will fly. However, I know there is an initial height maximum when undertaking the medical at OASC - I will try and find out on Monday.
There are some guys who fly fast jets taller than 6 foot if that helps?
An extract by Squadron Leader Mark Byrne from the BBC website says:
There are a number of physiological factors that determine overall suitability as a combat pilot in fast-jet aircraft. Height is not the full story, rather there are certain key measurements that will determine whether it is safe to fly in a certain type of aircraft.
In particular, the length of the upper leg (from buttock to knee) is critical in ejection seat equipped aircraft as it would sting like crazy if you had to eject in an emergency and shaved off the lower parts of your legs!
Seriously though, it is not just height that is important, body weight is also a factor which is taken into consideration.