Do you want a mono or colour laser printer?
For a mono compare the price of the printer with the cost of replacement cartridges. The toner cartridges for many of the cheapest ones cost much more than the printer.
A good starting point might be the HP Mono LaserJet 1022 (for around �110-120)
For colour printers look for ones that offer separate colour cartridges (black, cyan, yellow, magenta) so you only have to replace what's run out.
Decide whether you want one that prints just coloured graphics or photos. You'll need to look at the weight and quality of paper too.
A good comparison might be the HP Colour LaserJet 2600 (for around �210-250). There's a HP Colour LaserJet 1600 for around �110-130.
The difference between the 1600 and 2600 is that the 2600 is supplied with a full set of toner cats, whereas the 1600 only has a trial pack.