Wanadrive is a very useful and informative site, please take time out to have a read of it - particularly the chapters 'Myths' (number 8 being my favourite), 'FAQ' (pay attention to questions 1 & 7) and 'On Your Test' (and those 'Things to remember on the test').
Click on any of the chapters between 'Your Licence' - 'UK Pass Rate' and then go to the tab at the top titled '10 Reasons for Failing'. Do you do these mistakes on your lessons still? If so, then you should not be taking a test yet!
It also has a good online shop for you to stock up on material for your theory, so no more excuses!
Go on, take a peek!