I used Equitours many years ago and they were fine. Equitours has been around for ages. They tend to do their homework and check out their ride vendors to be sure things are up to snuff.
We also thinking of going to the WEG. Our plan is to rent a house in Normandy and get tickets. We found that driving around France is very straightforward. Of couse the food is great and there is lots of non-horse things as well. Normandy is a lovely area to visit. We did a riding vacation there (not Equitours) about 15 years ago and loved it.
We are going, and we are going with Equitours. Great service so far. But if you are serious, I would get in touch with them soon. They said they were almost sold out 2 months ago - so take that into consideration.