I just went for a cheap mono laser with the eco-unfriendly expectation that I would buy another one when the toner ran out. Actually I now find that replacement toner is not too dear - and there are compatibles if one wants to go that way.
The printer is a Brother HL-2130, purchased in Sep 12 for £46 from Amazon. The toner is still going, although it now advises that it is low - I guess I am not a 'heavy' user, but still not bad. It is connected to an airport express and works flawlessly over the network.
As an aside, compatible inks seem to have come on - maybe it's just pot luck - but I recently bought compatible inks for a Canon multifunction inkjet and they are excellent. Photo printing is as good as the original inks - even just renewed a passport with a home-printed photograph. At £4.99 for 2 complete sets of cartridges (versus £35 for genuine) it seems pretty good value.