There seem to be a lot of people on this thread describing their situations but nobody has offered any opinions in return.
So, here are my thoughts. Take them with a pinch of salt, but I was 30 when I decided to abandon my previous career and I'm now in my late thirties and a captain flying the 737 around Europe. When I look back on all the twists and turns I can see where I got lucky, where my hard work paid off, and where I ws just in the right place at the right time. But times have changed.
1967kev - Changing career is a huge call. If you're settled, think long and hard. If it's ATC you missed, seriously look at that option, but why not get a PPL to scratch that itch? Flying little planes around the countryside is some of the most fun you can have in aviation. If you get the PPL, check our the job market again, but still don't think the employment prospects merit the commercial training, you still have a PPL!
Momminz - Health is a small part of it. Most people can get a Class I medical. As you get older the initial commercial flight training becomes much harder for the majority of pilots. The old saying about teaching an old dog new tricks has some basis in reality! I know. It took me longer than my sim buddies to reach the same level of competency as those in their early twenties who found it far easier and are therefore perceived by airlines as a lower training risk. That said, age brings maturity, which is a quality that serves you very well in a commercial flying job. Your problem will be the hordes of youngsters who will be looking for the same 'first break'. Risky but possible.
ysbrydtawel - I changed career to start flying because I did NOT love my job. If you love being a postman, stick to that, cultivate that career, and in the meantime get a PPL to satisfy your flying desires. With a PPL and the right attitude, and age on your side, you will be able to gauge the employment market in a couple of years time. If things look up and your PPL revealed a hidden aptitude, then go for it - but remember: the airlines are mainly recruiting through the integrated courses and your PPL could be wasted if you are later forced to embark on one of those massively over-priced schemes.
Captainloulou - Arrgh. Tricky one. Put it this way and remember it's just one opinion: At 30, with financial security and no kids, I was prepared to take the risk of being unemployed for a number of years. Now, with kids, a mortgage and a lot to lose, I wouldn't enter the commercial flying market if I had the same decision to make. At my current age and seeing so many friends from my ATPL studies who never got flying jobs, I realise I am very lucky. But if you have a carefully crafted plan and family support, a bit of luck, and the right aptitude for commercial flying, you could make it work.
Overall, most people seem to be saying that money is not their motivation. Good, because you will not earn a great deal as a commercial pilot. Unless you buy a £100k lottery ticket into a cadet scheme you might do quite well, but for the majority commercial flying is quickly becoming a paid hobby!