SarahP and I camped there, cost was 214 euro for Saturday to Friday. We booked for the weeks so that we didn't have to take the tent down while we were riding since we weren't riding together, she was in the 80hr, I was in the 90hr. This was our first PBP and I wasn't sure when we'd finish and didn't want to have to set everything back up again when we finished the ride, especially if either of us finished in the middle of the night. Our tent is an Easy Camp 400 in which we had a double airbed with proper bedding rather than sleeping bags. The tent also has a separate space inside where we can set up a table and chairs. I was glad for the space given the rain on Saturday, it was nice sitting inside in proper chairs while it poured down outside.. We had a double burner stove for meals and a jetboil for making tea. We drove to the EuroTunnel on Friday and took the train (used Tesco Clubcard points), stayed overnight at Boulonge-Sur-Mer and then drove to Ramboullet on Saturday morning for our 1:15pm bike check. We checked into the campsite after we finished at bike check.
The pitches were pretty nice and you are allowed to have up to 6 small tents on them. The shower block had sinks outside for cleaning your dishes. If I camped there again, I'd take a kettle rather than the jetboil since we had electricity in our campsite. If I did PBP again, I'd probably look to get a group together and get one of their cabins.
The bar needed more staff on the Thursday night, when the kitchen opened there was a 30 minute queue for food and drink orders. Other than that, everything else was great, I'd stay there again.