In fairness though, 'mobile only' for an outfit like this is maybe not half as suspect as it might be in other cases. They probably spend a lot of time on the move.
I always go to a BMW main dealer as I like to get the BMW aftercare and guarantee.
Bought one years ago from an dodgy motor dealer and had nothing but trouble with it. Despite taking a successful civil case, I never got my money back as he just closed down the business and started up again with the business in his kids name.