Hell, if you are too old then I'm completely stuffed!
I'm retraining to go commercial at 30 and I've not even started my PPL (just got the money together for PPL->CPL-IR->ATPL...phew!)
After talking to BA recruitment and lots of other commercial pilots, I don't think it will be a problem at all....although when you finally get there, there'll be people 10 years younger than you earning almost twice as much (seniority is VERY important in BA). Not sure what it's like for cargo though...
Good luck!