An unlock code sounds highly unlikely, you ask him for an Official Invoice for the work and Unlock Proceedure, and a copy of the Unlock Code from BMW Motorrad to prove its existence, and are BMW Motorrad charging for this unlock code?
Took my April 2015 GS Adventure in for 24,000 Mile Service last week and had this retro fitted. The day before when I rang and asked if it could be done I was advised that they had to request/order the code from BMW. On arrival at Service Desk when asked to sign the job sheet I asked the receptionist if the Hill Start code had arrived, her colleague sat a couple of metres away (whom I spoke to the day before) checked his PC and said yes it had and it was then added to the job sheet. As per previous post shows on my invoice as Part C77.23.8.536.874. This would suggest Dealers do have to buy the code to input it?
Very easy to use, squeeze of the Front Brake Lever, not been able to test on a proper steep incline yet!!
I took the view that for the cost I paid it would probably cost more if I ever dropped the bike but more so, potentially injure my pillion partner. On a previous ride out with pillion on board I got backed up on a steep one car width incline by other traffic and it was a real challenge setting off again. Happy to share price I paid via PM.