As some others have said, pay a bit more for a name band.
Names like Toshiba, HP, Dell, Fijitsu, Sony, Compaq, Lenovo (IBM) etc all build millions of laptops and have a reputation to keep up.
Some shops, like PC World and Currys, have their own "no name" brands that you cannot buy anywhere else. Brands include Advent and Packard Bell.
These are usually very cheap, but often poorly made with quality issues. As an example, in the list of 9 laptops I mentioned above, see which one got 2 stars.
If you go looking in PC World or Currys the staff may push you towards one of their brands, probably because they get a bonus each time they sell one.
If you want some hands-on time with a laptop then Tescos now stock quite a few, also Staples (as well as PC World, Currys, Comet etc).