HHMMM, so I wonder if all those Bromptons by UK sellers on Ebay come in with UK setup?

From what I've read, the (bicycle) standard is somewhat based on hand signals and so if you drive on the left side, you use your left hand to signal, and UK the reverse. So being used to using hand signals in the automobile, it passed on to bikes. Of course, hardly anyone uses actual hand signals these days, unless you drive old vehicles without turn signals, so it might be a moot point.