I work in the IT industry, so i'll chime in with my 2 cents.
Personally, if it were features you were after then I would look towards Acer, yes their customer service might be a bag of s**te but the product is good. For £800 you'd get a cracking laptop. A good spec, and feature rich.
For reliability, then have a look at the Toshiba laptops. They have a moneyback guarantee that covers you for the life of the laptop. If you laptop dies / breaks not only will they repair it for free, under the warranty agreement but they'll give you your money back (ex-VAT) - Cant say fairer than that. Talk about confidence in your product.
Also, they have a cashback offer as well as a cashback offer for accessories purchased with them. I will have to double check whether that is just a business offer or open to consumers too.
Sony / HP / IBM are fine, and are good solid laptops, but, your paying for a badge. So if you've got cash to burn then buy one of those. IMHO, not worth the money.
Dell is the devils work, avoid at all costs. Complete crap.
Ultimately though, buying a laptop is like buying a car. Its very subjective, what exactly do you want to do with it, and whats the budget?
I'm i'll find a deal for you