Duchess,
it should not be too onerous to complete the training for the renewal of your SEP Rating (with whichever training provider you choose- it does not have to be a UK ATO) and then elect for LPC with an examiner administered through the IAA - applying for a EASA CPL through the IAA.
Unfortunately after contacting the IAA FCL dept, I have been told they cannot re-issue a Part-FCL CPL based upon a JAR CPL issued by the UK which has lapsed, therefore I have to conduct the training and test, and subsequently apply for the Part-FCL licence, in the UK. And round and round I go.