Bezzie,
Check out this site to give you an idea of what is entailed within the ATPL theory exams.
http://jar-atpl-notes.fateback.com/
Its a free site and a great amount of work has been put into it by John Durcan (the author). Alot of it is double-dutch to me right now but I'm sure with tutorship it all becomes clear!
Hope this helps.
Craggenmore