This answer is Definitely false
If you do ATPL theory in UK after you can do CPL/ME/IR in SPAIN and in GREECE, as they are mutual recognized.
It is not true that you have to finish practice where you did your theory ATPL.
I have confirmation from CATS (ATPL school UK) and 2 flight schools in Greece and one in Spain.
SO DEFINITELY YOU CAN DO ATPL IN UK AND DO TRAINING/CONVERSION IN SPAIN, IN GREECE OR IN ANY OYHER PLACE WITH MUTUAL RECOGNITION.