We went through this a few years ago. Our experience was that UK universities are aware of the EB but indeed clueless about how to position it, because they see so few applicants.
That can work for or against you, though. DD was offered 70/100 by Bristol (which normally doesn't throw easy offers around) and another RG uni, and 80/100 by the RG uni she ended up going to. Other parents told us of some even weirder sets of offers. (80 looks like a big number, but it's quite doable; it's probably the equivalent of A*AA in the English system. 70 is the equivalent of AAB, which I suspect will not get you into Bristol.)
Another thing to watch for is that the UK uni may sometimes ask for a high minimum grade in English. For non-native speakers this is understandable as their English exam is "English as a foreign language", but for the native English-speakers a slightly lower score may just mean they are not all that good at/interested in literature and doesn't imply that there will be any barriers to learning. DD's English was not her best subject and she got less than the minimum, but we wrote a letter to the admissions tutor and all was fine.
In terms of preparation, DD reported that she probably had a wider general education than her peers, but she took a little time to develop the UK study skills which A-levels prepare you for better. She ended up with a good 2:1 and did fine overall.
The European schools in general are fantastic and surprisingly non-political (small p). We were expecting all of the signs to be up in all 5 of the principal languages (that list varies by school), but very often it would only be in one. If the Dutch section is organising an event they will put the sign up in Dutch, and if you can't read it, well, you either learn to read it or you make a Dutch friend.