What IS true (and this is what R1Geezer in alluding to) is that Johnny foreigner takes his half-term holiday at a different time to us Brits. Since CentreParcs price their product according to demand and since folks want to take their kids to CentreParcs at half-term, it stands to reason that the holidays are going to be cheaper on the continent if you can time it right. Mrs Buildersmate and I exploited this loophole for many years until the baby-Buildersmates grew up and didn't want to do it any more. We only ever went to the CentreParcs in Holland - no idea about pricing in France.
The CentreParc offering in Holland was pretty much identical to that in the UK - it started there, damn it.
Being a true Tory, I'm surprised R1 doesn't understand the principles of supply and demand that lead CentreParcs to hike up their prices when the demand is high. The other way to look at it is to think of it as them reducing the price outside half-term times. My glass is half-full, R1.