I don’t follow Druidh’s logic. Motorcycle plates carry the same number of characters as car plates so you could fit your letters and numbers on but you would be contravening the regs regarding minimum sizing of the characters for a car.
There is also the small matter of having to have the plate illuminated – as your car has a full MoT as opposed to a daylight one then I assume the full illuminations for the vehicle are required at all times, whether they are actually in use or not.
I would also question whether an approved plate maker would produce an illegal plate for you (you have to show the registration doc to get one made up).