Is it too late to start training to race? Absolutely not. Is it too late to be an elite, national level, or pro? Unless you have very special genetics, probably. Doesn't matter though as there are different categories based on level and experience.
In the states we have USAC, you blokes probably have something similar in Britain that someone else will have to steer you toward. It'll likely break down the rules and regs, fees, list partner orgs, list races, clubs, etc. A good bike shop is also a good place to get info on the local competitive scene.
I started racing on a [censored] bike with a few key upgrades. You don't need a bike the guys are racing in the Tour. But a smoothly functioning bike, and here's they... that fits you well, is essential. Definitely a bike from a proper bike shop and not a big department store (those bikes are usually on par with the quality of bikes found in toy shops, but maybe things are different in the UK).
Other than that you'll need to ride a lot. How much depends on your goals, your available time, and your motivation. With regular training it may take anywhere between a few months and a year to develop the strength for your first race. If you join a club or go on competitively spirited group rides you'll quickly find your place in the pecking order. Weekly training could be 6-10 hours a week for some entry level racing fun, 10-15 hours a week to realize some more lofty aspirations, or even more. But forget about that 3 x 30 minutes of cardio a week nonsense, that's for civilians.[IMG]/img/vbsmilies/smilies/wink.gif[/IMG]
Cheers
PS. check the road cycling and training threads as well - there's a lot of helpful information and advice directly related to your question.
