If it's anywhere near you, Popham is home to Paul Ambrose, a very accomplished instructor (learned his teaching stuff as a 747 instructor pilot for BA). Popham is also a great location as the airspace is all immediately available for aerobatics (no transit time wasted getting to a suitable bit of airspace) and the atmosphere at the place is excellent.
I've flown with Paul a few times myself and can attest that he's not only a good pilot but an excellent instructor.
Here's his website:
Special Flight - Pitts Special aerobatic display flying and training from Popham airfield Hampshire