Here we go again! Sorry, but this subject does crop up incredibly regularly. If you do a search using the keywords 'too old', you'll find many, many guys like yourself asking this question.
There is, of course, no definitive answer. It largely depends on what you wnat to achieve, and how single-minded you are about achieving it. There is no doubt that you could make it to a major - our own Capt Pprune started (as an IT chap) in his 30s, and is now flying 757s for one of our larger charter outfits. BA and Virgin will recruit people well into their 40s, if they have appropriate experience (say 1000-2000 hours including some jet time), so it's up to you to get that experience!
You must take each stage in turn as your primary goal, without ever losing sight of the eventual aim. Work your socks off; GAPAN aptitudes, PPL, IMC, night, ATPL groundschool, hour building, multis etc, etc, until you are in a position to start looking for jobs. Air Taxi work, instructing, commuters, who knows? It's all valuable, and it all builds into a CV a jet operator will appreciate.
The downside is that it will cost you a great deal of money and time. £50k is not unreasonable, and 2-3 years' hard work. If you have a supportive (emotionally and financially) partner, brilliant. But warn them it will be a hard struggle, and there will be setbacks. How much do you want it?