Right then it turns out that my options are:
AGE RELATED PLATE: I would have to give up all ownership of the plate H7 TOD and it would be deleted for ever and then replaced with an age related plate.
PERSONALISED NUMBER PLATE: I could put another personal number plate on and I would NOT have to pay to put H7 TOD on retention

and if I sold my personal plate on then H7 TOD would be allocated back to the car.
So if I went for an age related number plate does anyone think that it would hurt the resale value of the car if the car could not have the original number plate put back on?
Thanks.