Quintin,

I spoke to ADAC Munich today. In short: carnet is possible, even for people outside Germany (in my case: UK). Deposit for my 5000 Euros bike would be 3000 Euros (about 2000 pounds). Non-refundable fee for the carnet is 150 Euros if you're a member in an automotive association such as the AA or RAC. Issuing time by mail is definitely less than 6 weeks, possibly as short as 1-2 weeks. I even heard of people who picked it up in person on the same day (ADAC Munich).

Bjorn