In reply to toasted: I briefly looked at doing a trade as a career, at 25 I'm too old for apprenticeships as well and I make more money working in a shop so I ditched the idea. How anyone survives on apprenticeship wages I have no idea anyway, unless you're fortunate enoght to be able to live and eat for free with relatives it's not an option for most people.
Despite all that naysaying it is obviously possible if you really want it, but the likelihood is you'll have to save up a) for the course b) a stretch of unemployment and c) a period of time working min wage (or less) as a plumbers mate/lackey to gain experience. Getting a foot in the door for the latter will be the hardest thing if you don't have any contacts in the trade. Getting the qualifications alone will be unlikely to get you a job as a plumber.