It's built on clay as far as I recall and lies very wet in the winter. I played in the winter a few years ago and lost a ball or two that had plugged just of the green. Lovely course and a good deal when it's dry
I would suggest that if they are offering that deal and the course is open then it's probably in a playable condition, it's a top quality track so can't imagine they'd open the course if it was in a non playable condition. At £25 a head, I'd go for it.