I fly at a certain neighbouring gliding club and have visited Challock often over the years. They have a great clubhouse with bar and restaraunt, briefing rooms, bunkhouse etc.
I have experienced some stange goings-on there though like people being told off for opening the hangar doors and getting the kit out too early in the morning. The tug breaking down at the beginning of the season and not being fixed for a month. And a friend of mine went there for the day and took himself off cross country for a few hours and when he returned at 4pm everyone had packed up and gone home. I don't know any other club where the duty instructor/pilot would clear off leaving an aircraft unaccounted for.
Soaring conditions are fine, although regularly suffer from sea breezes on good thermic days. The ridge isn't the most spectacular in the world but it works. As said, cross country options are limited as you have a choice of going west, west or west and when you do that you hit the London TMA but all the clubs around London are like that. For training and local flying it's great.
In my opinion the Southdown GC at Parham (Storrington) is the nicest club in the SE - if you can live without the winch. (No, I am not a member there!)