I see what you're saying Peter, maybe its just a UK thing, but car snobbery definitely exists over here. You're right, its got nothing to do with build quality or performance or anything, its simply the badge thats on the end of the bonnet. My other half's old housemate was very much like that, she was in the market for a 4 door saloon recently and basically didn't look at anything bar the 3-series. I tried to tell her that she could've gotten an equally well-specced Mondeo, Mazda 6, Passat, whatever, for considerably less but none of them were good enough! lol
I dunno if I could've afforded a BMW though, a 320SE costs near £25k once you've specced it up whereas I know you can get a Mk5 Golf GTi for about £17.5k.