You could also try West London Aero Club at White Waltham Aerodrome; close to J8/9 on the M4. A large grass aerodrome with three runways and home to the ATA during the war, the clubhouse was the ATA HQ. The club has a largish fleet of PA28 Warriors and dedicated FIC instructors who spend all their time with you. Not the cheapest , but you get what you pay for.