haha you are joking right?
http://www.caa.co.uk/docs/33/LASORS2005.PDF
Check out section C1, JAR PPL (A) requirements...i assume you arent talk about a helicopter licence, is you are it is section C2, but conversion requirements are the same.
You need to do a skills test on a SEP/MEP aircraft, you will also need to pass written examinations in Air Law and Human Performance and Limitations.
You'll also have to pass both written and practical exams for the Radio licence to be issued.
Get a JAR class 2 medical.
Pay £149...............apart from that, thats pretty much it.
HB