I don't know how big Wallington is, or how near London it is, but here is what I did:
o Find a mailing list, especially if it's local. Cincinnati (pop 300,000+) has a Yahoo Group. The files section holds a lot of local wisdom. There are ad hoc groups that do whitewater runs every weekend, and have an open invite. They also carpool to bigger meets and festivals (~200-300 miles away).
o Find a local club. With a big enough group, there are always a few that like to help newbies along. Bigger clubs may hold "meet at the beach", rolling classes in a pool, or intro classes. If there are physical meetings, go! Say hi, be polite, and you'll find someone who'll ask if you want to borrow a yak and tag along. Apparently it is not possible to own just one kayak, and many have the beginner boats they started with. If you do decide to buy, the club and craiglists are good sources.
o Find an outfitter, or someone who runs a livery. There are 3-4 outfitters within a half-hours drive, and 3-4 places that rent canoes. Stop in, say hi, read the bulletin board. Tell them you're not ready to buy, to keep the Boat Science in check
If you're considering building a boat, find a forum like this one.
Forgot one: the Sierra Club and the local Parks & Recreation commission hold classes. The P&R one is 3 1/2 hours one night a week for ten weeks, and is designed for beginners. I'll have to buy a pool pass, and pay the 'out of county' price, and it'll still only be $100 or so. They supply everything. The Sierra Club classes run the gamut from "Intro to Kayaking" to "Advanced Whitewater".