Hi there,
I can't tell you about unfrezing your spanish fATPL cause luckily I converted mine to an IAA before finding myself in such a nightmare! but I can tell you that in order to convert your spanish JAR-FCL fATPL to an irish JAR-FCL fATPL you'll need (as stated above) either be living in Ireland for more than 180 days a year or be employed by an irish company, and I'm afraid is gonna be the same with the UK CAA (though not 100% sure).
I recently unfroze my licence and got the IAA ATPL issued within 5 working days and got it sent to the address I told them, they even call me to let me know it was ready!
can you imagine that in DGAC?
Well, hope it helps, good luck!