BAsically I have 2 RST's one has a plate on I want to put on retention and sell (the car I want to keep) and the other has a private plate on I want to swap to my new car (then sell the car).

What is the best way to do this?

Put the plate I want to sell on retention 1st, then wait for all the paperwork to come through, then do the transfer. Or can it all be done together?

Dont mind driving to local DVLA office to sort it (so they can look at the car if need be), but dont want to if I dont have to, but they will probably want to see the car of the plate im taking off.

Any advice appreciated