Since this thread was started, I've aquired a Brompton, which I take in with me wherever I go, including shops, banks, supermarkets (where I fold it up and place it in the shopping cart), bars, hospitals and so on. I thought I'd run into at least some resistance, but almost everyone has been welcoming. Only Decathlon, the big French sporting goods chain (which sells folding bikes!), asked me to leave, and I fixed that by complaining on their Facebook page. A higher up got on the phone and told the manager who'd refused me entry that he was to allow any and all cyclists to come inside with their bikes, folders or not, if they wished to do so.

Chalk one up for us cyclists!