Motability make it very easy to do, as long as the new plate is personal to you they don’t have a problem with it
The cost for the plate is a one off and will vary depending on how cherished it is. You’ll then pay DVLA £80 every time you change it to a new vehicle, so once every 3 years unless you extend the lease.
Once you’ve brought your plate and receive your certificate from the DVLA, just phone Motability and they’ll do the paper work and you can then put the plate on you car.