New to Mudcat and just found this thread.
The prostitutes version was sung (and also composed as far as I know) by a guy called Rick Norcross, from Fort Lauderdale in Florida, who toured England regularly in the swingin' sixties. He also did a great round with Cripple Creek, and a fugue by getting the audience to sing a couple of different songs simultaneously.

What I remember of Greenstamps was:

There were two ladies of ill repute,
One was ugly, the other was cute.
The cute one, she charged quitw a lot,
But the ugly one, she gave green stamps.

Green stamps were all she gave,
Green stamps were all I got,
Green stamps for weeks I'd save
The I'd go to the cute one
and cash in the lot!