From what I can tell, RYA Keelboat Level 2 is about the same as ASA-101 Basic Keelboat or US-Sail Basic Keelboat.
For £30,000 pounds you could get a nice sailboat but I wouldn't recommend doing that. I would probably suggest buying a used sailboat in the 18-22' (5.5 - 6.7 m) range first. I would suggest sailing that for a couple of seasons. Then I would suggest getting rides or crewing on some larger boats.
Looking over boats.oodle.co.uk I see some reasonably good starter
boats for £5,000 and under. I see an 18'6" gaff rigged cutter. I see several Deck Polyesters, Dauntless 22, Atlanta Viking, Leisure 20 and 23, a 22' Anderson, Newbridge Navigator, Hurley 22, Nomad 22, Van De Stadt Splinter 21, Freedom 21, West Wight Potter, Halcyon 23, Sparta 22, Snapdragon 22, and several Corribee's.
In just checking over the used boats you can see what types of maintenance issues can turn up over time. Looking at them in person, you get exposed to different types of boats. If the boat looks good in person then take it for test sail and find one you are comfortable with. Once you find a boat you like, you can sail it and get experience. More importantly you find out what you do and don't like in a sailboat, what is important to you and what isn't. When you do decide to move up to a larger boat you will be much better prepared to find what you like.