If it's the non expiring type, you just need to fly with an instructor until they are happy to send you solo; no exams.
But remember, if it is a UK national (i.e. pre-JAA) licence it will cease to be valid on any EASA aeroplane in a couple of months time.
My comments above were based on a JAA licence; conversion of a UK national licence will involve a couple of extra steps:
Demonstrate knowledge of the relevant parts of the operational requirements and Part-FCL (an oral test combined with the proficiency check)
Demonstrate to a CFI or an examiner the correct use of radio aids (certified in the logbook).