Car dealerships are a breed of their own in British architecture. I don't know whether there are dedicated building regulations for them, or quite how this genus of the species 'bad architecture' has developed in the way it has. They always look uniquely clipped together and temporary. It is as if car dealership design has developed on Easter Island: you can see where it came from, but at some point it stopped having any relationship with the rest of the construction industry.
The constructional logic is derived from the sign - a structure with clipped-on symbols. Like all buildings like this, the cladding system is a law unto itself with strangely small panels contrasting with the over large and annoyingly reflective glazing. Look at the picture above: in its vertical expression, there is no hierarchy between glazing member, structural column, downpipe and advertising hoarding.
This is unreal architecture, the same wherever it appears. It embodies nothing about BMW, nothing about the excitement of the expensive machines inside. It's the kind of building that shoddy planning authorities allow to pollute the roadside when they can't think of anything else to do with a site.
By the way, I love that this super-generic building intended to promote carbon-guzzling machines is in the same town as the godmother of eco developments, BedZed. Way to have a joined-up strategy, London Borough of Croydon.