PC World will match on-line prices. I think I would buy one from Dell though. Check the output sockets. I would be inclined to go for Windows XP rather than Vista.
I've been looking for a while too...The Sony VAIO's seem to be appealing the most to me - except the price. The same spec'd laptop from Dell is about £150 cheaper. But I like Sony stuff, so I've been shopping around on price and www.dabs.com is pretty good, as it www.empiredirect.com Do your homework find the laptop you like then just type the model into google, and go through all the places that stock it to get the right price.