The only 'small grass airfield ' close to Farnborough in those days was Fairoaks, but that isn't in the middle of houses although it does undulate. Could it possibly have been Queen's Parade, the army polo field just south of Farnborough? Or for a long shot, maybe it was Woodley? I discount White Waltham because once again it's not surrounded by houses (mostly).
Another long shot; Bray Court just outside Maidenhead was once used as an ATC gliding school which would have had Sedburghs. I don't know much about it but it could have been surrounded by houses.