In reality the delivery time of 6 weeks turns out to be 5 weeks for most UK customers. That was my experience plus others I have read here too.
The MS calandar week numbers can be 'adjusted' in the settings. International companies have 'to agree' which is 'week 1' every year. I dont know what BMW use but it will be the same in US and DE
I am sure the delivery weeks will tick by quickly....