I'm sorry to hear about the damage to the aircraft.
I'm somewhat surprised by David's remarks about instructors thinking its chicken to tie down 'planes. After all if the aircraft are damaged in strong winds there's nothing for them to instruct in, and they won't get paid.
At the airfield I fly from (Wycombe) the tie-down rings are actually 'built-in' to the apron, and all club aircraft parked on the apron overnight are tied down (its one of the Duty Instructor's jobs to make sure its done). If storm force winds are forecast then they always try to get as many aircraft into the hangers as possible.
There was a report on the local TV news last night that a mini-tornado had been reported in the vicinity of Northampton, so I wouldn't be surprised if something similar had blown David's tree down.
Brooklands