Hi, I wrote a Newsletter article a couple of months ago, about buying a computer on a budget. It does warn you to avoid buying anything beginning with the letter "A" (Acer, Advent, Asus. But ignoring Apple and adding Packard Bell - owned by Acer).
However, it didn't go into detail about where to buy from. PC World are OK but will try really hard to sell you add-ons and extended warranty as that's where their profits are made.
Avoid Laptops Direct as they may sell you the "wrong" laptop and then you'll struggle to return it. John Lewis is a good suggestion as their after-sales support shoud be great. Otherwise use Amazon.