Adam,
I will admit I don't know much about the British forces, but they always seem to be cutting back rather than expanding, so I guess they can afford to restrict the pool of applicants.
In Australia, the age limit for RAAF entry is 45 (they prefer <27.5 but I know of at least one 34 yo pilot cadet). In the RAN the age limit is 49 and in the Army Avaition Corps it is 52!
Food for thought.