Yes, have to agree with Brandy on this. I'm careful about clients seeing my car too and when doing an outcall to someones home I always try to park down the road from their actual address. Doesn't always work though as some do watch out for me and notice me drive past and park down the road!! I don't even park my car outside my incall flat (and there's plenty of parking too!). Luckily there's a nice free car park just down the road and I park there and walk the couple of minutes to my incall flat. Some guys can be quite nosy where cars are concerned and in the past whenever there's an upmarket car parked outside (not mine, and not always right outside my flat) the assumption often is that's its mine - ie., "is that your BM/Mercedes/Lexus etc etc" outside? So, as Brandy so rightly points out, there's always the danger of a client noting your car registration and doing some digging. Even if I did park outside my flat and was asked if that such and such car was mine I would deny it!
For example, at one time I used to park outside my flat and a regular client once asked me what my real name was to which I gave my usual evasive answer. His reply to this was "well if I really wanted to find out I could, I know your registration is ........... (unfortunately he did know my car) but I wont". He was just being flippant at the time but it made me realise how stupid it was for me to (a) let anyone know what car I drive and (b) to park outside my flat. So be warned all you ladies (and guys) who drive, keep your car well out of sight.
Although I'm not sure how easy it is for someone not employed by DVLA, Police, etc. to get that information. Maybe someone could enlighten me on that one.