Agree with WFG about Godstowe. We looked there too. At that time there were lots of day girls and occasional boarders which slightly put us off. Plus does Godstowe have Saturday school. I know not everyone will agree but as we thought as overseas parents that Saturday school was important as it meant they were busy in the morning and then had matches in the afternoon or activities, but still had Sunday to relax etc as two free days even with activities can be hard to fill.
Thanks for all the comments! I was wondering when did you look at Godstowe? They have told us that they are increasing their number of foreign students and that there have been more boarders in the last year. Godstowe received incredible reviews (also in the Good Schools Guide) recently and one thing they have is an ESL program. Still ... Ashdown is beautiful, seems very warm and has superb teachers. This is a really tough decision.
This is the first time I heard of Windlesham house school so thanks for suggesting that!