Driving Standards Agency Lots of useful information and you can book a theory test online. There are also mock theory tests and lots more.

Pass Plus is a scheme backed by the Government's Driving Standards Agency and insurers to encourage newly qualified drivers to become better drivers. Pass Plus gives extra experience and positive driving skills that would otherwise take a long time to acquire. Pass Plus consists of an additional course of six specially designed training sessions to follow on from a successful practical driving test. They cover driving: in town, out of town, in all weather, at night, on dual carriageways, and on motorways.

2pass. "Everything you need to know 2PASS your driving test and more”. One of the best learner driver sites in the UK.  Free information on both the theory and practical tests.