Well, a fellow PPL student is currently on the Cathay Pacific Cadet scheme. I thought he was wasting his time filling out the application form - he was 35.
He's currently in New Zealand - training with Cathay Pacific. He'll be nearly 37when he finishes.
If its good enough for Cathay Pacific then I'm sure that the thirties are just fine.
Another chum was 41 when he started his ATPL theory - now flies Biz Jets.
Another is a Training Captain for EasyJet - PPL and instructing from age 34 - F/O for EZY aged 39.
I can think of another 2 who started at about 34 and are now F/O's - one at Jet2.com the other Ryanair.
Sure by the time I get to be 60 they'll have upped the retirement to 70 so I've got 33 years flying ahead of me.