Wouldn't it make more sense to start with the JAR writtens, and go on from there? For that you just need a PPL.
I haven't gone into this in great depth but it seems to me that there's no 'conversion' of a FAA license to a JAR license per se. The last time I tried this sort of thing, in Germany pre-JAR, I got a CPL/IR for my FAA ATP after doing Air Law, Mass and Balance, and two other writtens I cannot remember much about. All in all it struck me as a lot of work for not very much in return, and that was with plenty of hours.
I was amused by being told that I didn't 'have the necessary experience' to even do the ATPL tests because I didn't have any time in Part 25 aircraft. So then I asked in return if I could fly a Citation on a CPL, perhaps? 'Of course not! Zat is a Part 25 aircraft!' So what was that CE-500 Series type-rating on my FAA license good for then?
Well, that was just me being silly, of course. The real answer was just 'Please go away and stop bothering us.' So I did, ending up flying in Africa as a Captain on an aircraft the Germans wouldn't have even allowed me into the cockpit on, since one needs a frozen ATPL as an FO.
It's a Euro-centric little world you are trying to break into and FAA qualifications seem simply to annoy. If it's JAR you want, perhaps it's better to just go JAR from the beginning.