Thanks Stig, errm, could you be THE Stig...?? The one who went off the aircraft carrier...!! Anyway, in the meantime I've had a reply from the company which did the check..
Although AutoCheck is as comprehensive as is currently possible, it may not reveal that the vehicle has been declared a write-off if the owner was self insured or third-party insured or if the vehicle was not covered by its insurance policy at the time of the incident (and the AutoCheck Report Insurance will not cover this risk). If you are still worried about the vehicles status we would advise getting the vehicle physically inspected.
That confirms what you wrote. It has passed three MoT's since the re-shell so it can't be that bad. If I buy it I'm getting a body only half as old as the rest. Many thanks.