The cost of the theory test is currently £31. (Price increased April 2009)
You can buy books and Dvd's from any bookstore. Look for the DSA symbol and make sure it it the "official" publication.
You cannot take the theory test until you have got your provisional licence and you are 17 years old.
It is best to study for the theory test whilst you are taking lessons as this reinforces your study.
You will have to pass the theory test before you can apply for a driving test. Click the link below to book a theory test.
http://www.direct.gov.uk/en/Motoring/Motoringtransactions/DG_066356
The cost of the driving test is currently £62.00 (Price inceased April 2009)
Your driving instructor will be able to tell you when to book your driving test. He will give you his ADI number which you will need to complete the booking.
It is worth remembering that it costs anything from £150 if you fail a test. The test fee, the hire of the car for the test and a few lessons after you failed all add up. Be a savvy learner and make sure you do the work before taking a test not after.
Click the link below to book your driving test.
http://www.direct.gov.uk/en/Motoring/Motoringtransactions/DG_066356