There are many publications available, I would recommend the D.S.A books and DVDs as the D.S.A is the government body that sets and conducts the tests. Below are links to websites that you might find useful...

The Stationery Office Official government driving publications

Driving Standards Agency Responsible for conducting driving tests in Great Britain for cars, motorcycles, lorries and buses.

On-Line Practice Tests The DSA official online mock Theory Test questions covering a variety of topics