Take a TVR mechanic with you who knows the Speed Six engine . Get it up on a ramp and check the chassis, check for damper leaks and check tyres (if its been sat for years may have caused problems). Tyres need replacing on age.
I would ask if the speedo works OK, as many transducers work only intermittently.
If that's the case, then the mileage may be higher than indicated, because if the transducer isn't working properly, it doesn't record the mileage, too.