I've just posted this on the Thank-you Evesham thread so I'll reproduce it here.
Kev and I tend to shop together, on many occasions at Computer Fairs I have asked a question only to have the sales person (usually middle-aged and male) address the reply to Kev. Kev's response is too look at them blankly and say "Sorry, I don't have the faintest idea what you're talking about, you'd better talk to Penny." which never fails to leave them open mouthed.
BUT ... actually I haven't found shop staff to be patronising, not recently. In the past, in the big shops like PC World, they were but these days they are much improved.
I have, however, found some helplines (the ones run from a call centre full of non-tech people) to be extremely patronising but that is mainly because the person at the other end is running through a set script and the conversation would be the same whether I was male or female (I think....).