I'm afraid I completely agree with Hatrick.
We were at Longleat for a weekend at the end of the February half term and I have never seen it so rammed full of people - to the point where I didn't particularly enjoy the break at all.
We would go to the pool at 10.00am and by 10.30/45 it was absolutely heaving. The only time I would go swimming now is after about 7pm. The Jardin de Sports was busier than I have ever seen it as well. Whilst there, I bumped into someone I knew who agreed there are nowhere near enough facilties to cope with the place when at full capacity (although I don't remember it being so much of a problem before the huge amount of new accomodation was built).
We've been to the various Centerparcs many times, including six visits to Longleat, almost always during school holidays, and I don't think we will be going back for a while, if at all. It's a shame because we used to love it. Also, given the amount of money it costs and the amount of spending money required, I just feel it's simply not worth it.
Also, they seem to have changed the terms of their 'loyalty' voucher scheme without telling anyone - in fact, I heard it was being phased out completely, which wouldn't surprise me.
To be fair, we had nice (but pricey) meals in Strada and Huckleburys and also the Sports Cafe food was OK and reasonably priced. Also, my DD and her friend really enjoyed the 'outing with owls' encounter. Apart from that, I can't think of anything else that was good about the experience.
Sorry to not be more positive.