Regarding renewal of your SEP rating, which is what needs to be renewed; the licence itself being non-expiring, the CAA website provides the following information:
"You will have to go to an ATO where the Head of Training will determine how much training you may require before completing the proficiency check (LPC).
The amount of training to be done depends on many aspects such as:
the last time you have flown the aircraft
your experience
the complexity of the aircraft
When you have completed the training, the ATO needs to issue a completion certificate which you can present to the examiner before completing the LPC."
https://www.caa.co.uk/General-aviation/ ... s-expired/I cannot answer the PMD question.