I dislike PC World immensely. I had a laptop from them which broke within 9 months. Sent it back to them (warranty, yay!) to get it fixed, telling them what was wrong with it. It then takes them 2 weeks to tell me what was wrong with it (and I was right) another 2 weeks to return it to me (without a power lead) and then 2 MONTHS to get my power lead back. So PC World are ok, until you need to contact them for any help. And they overcharge a wee bit, and are quite good at selling you stuff you don't really need. But apart from that, they seem ok.
As for the main question... online retailers are quite good. The one's I'd advise are
http://www.ebuyer.com and
http://www.overclockers.co.uk
For your needs I'd say the one below is a safe bet, but as people have said it's a good idea to have it in front of you and have a play around with it first.
http://www.ebuyer.com/product/139121
Also that one doesn't have an ATI/Nvidia card, which you WILL need if you want to play any games. Here's a couple I'd advise:
http://www.ebuyer.com/product/138876
http://www.ebuyer.com/product/140406
The first has a bigger hard drive, but slightly worse graphics card. But if you don't want to play games, either would be good enough, so I'd go for the bigger hard drive. And as ACtheTROLL said, you can spend your extra few bob on a whacking great big external hard drive. You can get a large 500GB for ~�55, or a portable 320GB one for ~�78. Have a look around for some good deals.
And yes, laptop = notebook