This is a damn good question Jim Panzee
On paper you should say you're uncomfortable answering that or you don't want to talk about yourself but personally I don't want to make paying for sex with a stranger feel anymore awkward than it already is. People who like waffling on and talking a lot don't like to be stopped from doing so directly (even if you're paying for their time), so just guide them and nudge them into talking about themselves if you can't get them to shut up. Bring up that Channel 4 prossie documentary or something and ask what they think about it, or bring up other gossip. I would normally prefer not to know anything about the WG because if they sadly get a stalker in future they'll know it's not you. But if they like talking about themselves then they probably talk to most people they see and it's their decision to pass on personal information.
I don't like awkwardness during a punt. So what I do is have a false name, job and home. Three simple facts that are easy to remember (even when you're banging away) and stick to. They are similar enough to the truth that if I ever meet up in civvie life I can claim she misheard me. Also I know a bit about the town and job so can talk about that.
I'm actually more than happy to talk about my reasons for punting, relationship status, and my past sexual experiences and other punts with a prossie than I am with a civvie. At the end of the day what are they going to do with that information if they don't know who it's about? This is a nice ice breaker for bringing up anal etc. for me anyway.
I sometimes get taken aback by clever independent girls who get curious, when I don't have time to concoct a lie on the spot without it looking like I'm lying. So e.g. someone knows my true town, another one knows where I went to Uni and how many family members I've got, another knows a bit more about my job but not enough to find my employer, one knows a hotel I booked and two saw my number plate, one of them pay pal details (as false as I could get away with), another I sent an internet banking payment to. All of them have a good idea how long it takes me to reach them.
But at the end of the day they're not all going to get together and join the dots unless I become a billionaire, and that ain't going to happen to someone as paranoid as me. If the WG values discretion (e.g. if they have no face pics or only face pics in their PG) then they don't want to get found out anyway themselves, so telling them anything you like is unlikely to do any harm. The ones that do show their faces probably see so many guys you've got nothing to worry about anyway as she'll probably forget you.