Hi Barry
My thoughts exactly these codes are part of the vehicle and should be handed over at the time of sale and the owner able to keep them like the radio code. Vauxhall have done it for years with the car pass.
Yes i know they get lost once the car gets a few years old but the dealer should release them to the owner of the vehicle upon production of the v5 and proof of identification.

If all customers were like one of mine who went to but another VW armed with info from me that it would be prudent to get the security codes at the time of buying the car from the dealer so i could continue to do all his work and him not have to return to the dealer. The long and short of it was the dealers said they could not give him the codes so he walked and did not buy the car, he went to another and through the network bought the same car and was given the codes as they realised it was the difference between money in the bank or not.