Hi Mick,
I too had difficulty in being able to get new keys at a sensible price, and so the first couple of spares I purchased were through Clipper Marine, the UK Bavaria agents. I don't remember how much I paid, but a couple of years ago after trying various locksmiths I found a guy with a locksmiths stall on our local market. He took one look at the key I showed him and he said yes he could make new ones and "which boat was it that it came from" I hadn't suggested anything about where it came from so was surprised at his question. The upper key shown in the photo below was one of the ones that Clipper sent, while the lower key is one of the new ones made by the market trader. They are identical other than in name. If I see the guy again, and he does not always come by, I'll try to get a contact name and email address from him and post it here.