Hi Pilot16,
The time lines are thus:
Pass ALL 14 written exams within 18 months of the first exam being taken.
Obtain a CPL/IR within 3 years of passing the ATPL written exams. If you don't then the exams will be invalid and you will have to sit them again.
Obtain a full ATPL (1500 hours) within 7 years of your JAA CPL/IR (fATPL). This of course requires 500 hours of multi crew aeroplane experience, so you'll probably have to have a job for at least a year or two during this period.
Information contained within LASORS Seciont J 1.7 (on Page 7):
http://www.caa.co.uk/docs/175/Lasors_Section_J.pdf
Best wishes,
Charlie Zulu.