I found Escortguide.tv to be very useful in France - the link is below. I would also use it for the rest of Europe, other than the UK. Most reviews are not posted in English, but some are and others are available in translation. Either way, once you figure out what the different entries mean in English, you can work out the scores and services in other languages.

Some of the ad sites, like 6annonce.com, also have reviews. My experience is that the same rules apply to them - if the reviewer is established and the provider has a number of reviews with similar information, you can count on the reviews.

The whole business is very different in each country depending on the laws. In France, it is legal to provide, but not to pander. The high end of the business is completely dominated by traveling, Eastern European ladies, working for services based in Eastern Europe. Screening is non-existent, though my guess is there is a big strong guy in a nearby room who will kick the crap out of you if you cross the line. Anyway, it is not that hard to find a couple of decent agencies. It is not a sure thing that every girl working for those agencies will be a winner, so you still need to check for reviews, but for the most part you will do okay. I would suggest an agency or two, but a lot of them come and go. Escortguide does also rank agencies, so you can start there if you want.

Hope it helps,
Zig