i beleive (not 100% certain) that there is some way of getting around this by taking an FAA class one medical and then converting it to JAA. i don't think the FAA have any pre-set prescription limits (just have to be correctable to the set standard - makes a lot more sense than JAA!) so you should be able to get an FAA class one (they have medical examiners in the UK i think). then when you have the FAA class one you convert it to JAA - the medical for the conversion is equivalent to that of a renewal so you should be OK. i'm not entirely sure about any of the details - i've just picked this up from posts on this forum so it might be worth looking into this option further by doing a search on the topic. good luck
cheers
Rod