After 10 years away from military aviating I used the Trevor Thom books (bought 2nd hand on eBay and then re-sold for about the same money) to do some self study and passed all of the exams without too much trouble.
If you want to find out what level your brain is currently at then may I suggest that you try
www.airquiz.com - for just a few quid you can find out what level you're at and get an idea of what you need to do.
Any questions PM me - all done this year so still fairly fresh.