You can design your own route in Google Maps on a PC/Mac and then send it to the car. You need to have a GMail account, be looged in, and have got your BMW Assist account set up. Google maps contains a 'Send to Car' function, and you need to tell it the car type and Assist user name. The route will appear in your 'Messages' list. It's easier than trying to do it in the car, and works with full UK Postcodes too. It's the only reason I have a GMail account as well.
You can even share it with other BMW Owners........should you wish to. Handy for Club drive outs on summat like a 'Champagne Run' or 'Ring' trip say. Everyone uses their own route to an agreed meeting point, then all onto the same route from there. Of course you need an up to date CIC Nav and a current Assist Account...
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Note - it does not work from a Tablet for some reason or other...at least it doesn't on the iPad. It used to work on everything without an Account, but alas no more.