I don't buy IMR but the best online stores for batteries I have found in the EU are:
nkon.nl
ledfiretorches
flashaholics
If I'm not wrong ledfiretorches has free EU shipping below a certain price. Nkon has probably the cheapest prices though they charge for shipping so if you buy just a battery or two the price might end up being the same or higher.
They all sell some IMR batteries, not sure if the prices are competitive but for Lio-on protected batteries they have the best prices I could find. You could possibly check Amazon.de and Amazon.uk and ebay to see if they have anything at a good price. From my experience batteries Lio-on batteries tend to be more expensive from German resellers and cheaper from UK resellers, at least now that the pound is low but is worth searching carefully.
Hope that helps.