Actually, you'll find bathroom attendants in lots of bars in Central London (particularly Soho), both gay and straight, and certainly not pretentious places. I was of the impression that really they're there to make sure that people use the cubicles to neither (a) get off with each other or (b) do drugs.

When I was younger, I used to feel a lot more uncomfortable about not leaving a tip, but as I've become older and slightly grumpier, I've got no problem using soap and paper towels, even if they are supplied by the attendant, and not leaving a tip. Every licenced facility in the UK is required by law to supply a toilet, soap, running water, and a means of drying one's hands. It's not like they're doing me any favours; they're obeying the law.