Use Form 1104 (here)
http://www.caa.co.uk/docs/33/SRG1104Issue10.pdf
to convert your Licence to an EASA one before the 5 year expiry date.
Only current ratings can be transferred over though, so go to your local flying school and get your SEP/IMC renewed.
The IMC will appear on the EASA licence as an IR(R). This is just a new name for the IMC to fit in with EASA.
If you don't renew expired ratings, they will be printed on the back of the licence, and you can renew them later. You will have to re-apply to the CAA to have them transferred to the front of the Licence before you can use them again though. (For a fee of course!)
MJ
