Buffalo 802.11n Cable/DSL router for £29.82 delivered. This router is as solid and reliable as they come.
Note: They are also available a couple of pounds cheaper from Ebuyer or Kikatek, however adding postage drives it over the cost of this deal. But if you already have an existing order to put in to either of these though then it works out even cheaper than the Amazon deal.
It can (and should) be flashed with the DD-WRT firmware, which basically turns this into the most fully featured router you can get your hands on short of spending an absolute fortune on corporate scale gear.