More good advice Jazz thanks. I know I'm not going to get the definitive answer - I'm just after a good starting out point.

I know there is an argument for building it first but the last thing I want is to get the machine built, then have to wait for a week or two before bits turn up. When I was a young'un I got a computer for Christmas (286 12mhz - Total beast.. 1 meg of ram!) I opened the box and they'd forgot to put the keyboard in. It was over a week before they opened and all I could do was play a shooting game with the mouse (keyboards were expensive). I don't want to go there again ;)