My airline got me a Dutch JAA medical to go with my Irish JAA licence (which comes with a German JAA RT licence), on which I hold a Czech JAA type rating, for which I did the training in JAA member Greece. - Notice the JAA in all this? All the above mentioned countries have apparently no problem with this procedure.
The CAA (UK) would accept any JAR medical, they confirmed, airlines generally don't seem to care.
But make sure that you call the appropriate CAA before you undertake any of this. - Your CAA may want to hold the full medical report, as in my case.
IP