I'd recommend several things.
The first is self-help. If you google it you'll find innumerable Web sites, or you can find books in your library or buy them online. The premise of most of these things (and of CBT) is pretty simple: get some perspective on your OCD, realize that it's irrational, challenge your irrational behaviour (by doing some experiments to see what happens if you don't do things a certain number of times), and ultimately change your behaviour. Sounds simple, but it's very difficult: you have to overcome years of mental programming. To do that you might need support.
So the second stage, if mere self-help is not enough, is to visit your GP. Depending on the severity of your condition, especially the degree to which it impairs your ability to go about ordinary life, your GP should (according to government guidelines) offer you CBT with self-help, a more intensive sort of therapy, antidepressants, or some combination of these. Although what you actually get will depend very much on funding provisions in your area and the attitude of your GP. If the first GP isn't sympathetic, try another.
The reason I recommend self-help first is that, one way or another, you'll have to overcome it yourself. The GP route merely offers additional support, some of which carries risks of its own (antidepressants in particular). Additionally, by helping yourself you'll avoid having OCD down in your medical notes, which may come up if future employers request a medical report.
For reference, you can find the guidelines on OCD here:
http://guidance.nice.org.uk/CG31/?c=91523.
The charity OCD UK has a list of self-help books here:
http://www.ocduk.org/2/books.htm. There's also a lot of other useful material on their Web site.