Constance is a smaller collection of quality hotels. After a great experience in Le Prince Maurice, I arrived in Belle Mare Plage with expectations of a quality hotel. With lower rates and 256 rooms I did not expect it to be near Le Prince Maurice level and I was right. The experience is very good, but not at the same level. The arrival experience was fine with a drink before being escorted to the room. I stayed in a junior suite, and it was quite nice with a good design, but nothing special if you have been to a lot of great hotels. My only complaint about the room was the bed which was horrible and hard.
The most important thing in a hotel is always the service, and Belle Mare Plage was good. Le Prince Maurice was, of course, better, but at a much higher price. This hotel is especially good for families or people that like golf as they have a great golf course connected to the hotel. The other facilities were good as well.
UPDATE 2014: It was overall a fine experience at Belle Mare Plage in 2011, but the new LUX* Belle Mare is in a completely different league and a wonderful experience.
My opinion: Good experience.