Quite simple really.
Renew your UK SEPL with a registered training facility or ATO whatever is most convenient or your choice. Renew your medical with an AME, again straight forward unless you have a medical issue (google search CAA AME list) there are many in Scotland and throughout the UK. Then apply for the EASA PPL submitting your expired JAR licence to exchange.
If you had a UK radio licence before, then this will be all that's required to give permanent RTF privileges included in your new EASA licence. Otherwise you will need to undertake the RTF practical test.