I have visited a handful of MPs and all have been discreet establishments where I slowly found out what was on the menu, which was limited.

Recently, I happened to visit one MP where the rooms have a sign saying "we do not offer sex, please don't ask for it". That was the one place where the offer came out plain as day in the shower room. FS? No problem...

Gotta love the plausible deniability...

not that the disclaimer will help them out one bit if LE shows up.

Another good indicator is a sticker on the front door that says that they donated to the local police officers' charitable organization.  That one may, in fact, do them some good.