I can now confirm that I have indeed bought a written-off Dax Cobra. My intention is to use it as a donor for a new Dax kit. It has an age-related plate but there is no V5.
For evidence, I could show DVLA photos of the car, also I will have the registration number and also the old VIN plate from the chassis, which will have been scrapped.
With this, do I stand a chance of getting another age-related plate? (