You can arbitrarily sell license plates in the UK?

Yes you can, and brokers take large ads. in our Sunday papers listing numbers, or you can buy them from the licensing authority. They also have auctions, at one time the prices were astronomical, but it's died down a bit.

Each time you move a plate from car to car, you have to pay a transfer fee of around £80.00

My reference to "losing" a number plate was sarcasm, how can the licensing authority, who are supposed to be able to tell a police officer instantly, on the phone, who a plate belongs to, lose A1, which was the first number plate given to Lord somebody at the inception of car licensing!