Ok spoke to DVLA and DVSA and story is as follows.
If vehicle is over 40 years old get the V5C changed to show "historic class" if not done already.
If vehicle is due a "tax" and not changed to historic go to Post Office and they will amend class there and send V5C to DVLA and "tax" for free while you are there. New V5C back in 4 weeks they say.
If V5C is showing "historic" and mot falls due you dont have to do anything as the system will show it is exempt automatically. So basically ignore it.
Spoke to DVSA and they say if vehicle is exempt for MOT but you get one done then if it fails you will need to get it retested to pass before you can use it.
If you arent sure then pay a garage to do a pre-test instead I guess.
Thanks for that.
Will check the day after the current MOT expires to see what they say about it on-line, to be sure.
As said, no MOT, no TAX, insurance is something like £150 for unlimited miles. Just add fuel.
Cheap motoring really and the Stag doesn't drive like an old car either, rear trailing arm suspension, mcpherson front struts, servo disc front brakes, power steering, lecky windows, adjustable steering column, laminated glass, crash design etc etc. Relatively little progress in over 40 years really compared to the previous 10!