To the best of my knowledge, I think the whole IR has to be done in Greece or the UK. You can not start the IR in one country and complete it in another.
If you do the 30 hours sim time in the UK, you will have to redo the whole IR ( 55 hours in Greece). Check with LASORS first before commencing anything.
I am in a similar sitiuation where I was going to have the CPL issued in the UK and then do the 63ish hours ME/IR in Greece as you get the whole 55 hours in the aircraft.
Hope that helped.