There is currently no legal JAA/CAA requirement for the PPL theory to be done in any formal manner, unlike the CPL/ATPL.
Though one day this informal arrangement might well end.
As Speedbird 001 states get the books - Thom - very good,
then self-study as time permits.
You will have to take your PPL exams with an approved ground examiner, usually your flying school. You must pass all exams within 18 months then you have another 24 months to get your JAA PPL. (Refer LASORS C1.3)
I don't understand the building 50 hours after the exams. To hold a PPL you must have passed the exams, or do you mean do all the theory then start the flying?