Unfortunately, that's the way it is. Your state of medical issue must match the state of licence issue. for renewals, any JAA medical is fine. I believe the British do the same.
HOWEVER, no need to go to Mater and do a new one. - Call the aeromedical section, they issued me an Irish JAA class 1 for free on producing a different JAA medical. (Come to think of it, the other one wasn't even JAA.) - If they don't do that anymore, all you need is an Irish renewal, not an initial.
Hope that helps, IP.