I see no difference between MED(H) and MED(A)...is there one? A class 1 is a class 1 and as Whopity says the you can only hold 1 EASA medical and it is that state that administers your licence. Based on the fact that you have held in the past a CPL(A) (with bells and whistles) 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. There are several ATOs in the North and Republic who could do this for you but should you wish to renew your ME/IR bits then you'd need to head south to Dublin or Cork to do this. When everything is in place you can SOLI to wherever you want, but again I suspect that would require both (A) and (H) bits to go together.
As has been suggested, give Simon a ring at the IAA - helpful and knowledgeable chap.