Hi Andy. Welcome to Pprune.
If your Licence is a PPL, has your SEP Class Rating actually expired? If it has:-
What you need to do now, is visit your local ATO/RTF (Flying School) and ask the Head of Training(HoT) there to asses what, if any, training you need to do to be recommended for the Renewal Flight Test with an Examiner.
When you have completed the training, if any, the HoT will sign you a Course Completion Certificate, allowing you to take the Test.
The Test itself is much the same as the one you took to get your Licence in the first place. The only difference is that the Nav. section will be shorter.
After a sucessful Test, The Examiner will sign up your Licence for another 2 year period.
MJ