Which PC for £500

If you're including a monitor in that, you're only leaving about £200 for the PC itself. Maybe something based on the Intel boards with the dual-core Atom chips soldered on. They'll take 2GB or more of RAM, have (non-3D) built in graphics and cases/PSUs for them are cheap too.

Thanks; unfortunately I don't really know what any of that means. If it was a bike I was asking after I would be the person who doesn't know what a bottom bracket is, possibly not even what a saddle is. And I would not know that some bikes were steel and others aluminium.
Basically I want someone who knws what they are talking about and understands what I am looking for to say, here, this is the OTP for you. I don't mind if I end up with a Langster, a Fuji or a Pompino as long as I can get from A to B. I just don't want to end up with a Unipak.
All I want it to do is surf the net, upload pics and, if possible, music too. No need for any graphics or games or anything else really.