I would say that it may be worth concentrating on the guy you buy from and who will sort things if they go pear shaped rather than the specification (IMHO)
All these laptops will perform, some better than others, but at any given price point the difference will be marginal
HP have a good reputation
However, I'd be inclined to go for Dell or Evesham because of the service if you have a problem. We bought a laptop from Dell at £329 early in 2006. It goes fine. It ain't super fast, but it works. If you buy from a high street retailer you have another step to get a problem sorted. Ask Comet what happens if your laptop goes wrong.