If it's for work, would your work supply a printer and inks for you?
Black and white laser printers are traditionally the cheapest to run. Colour lasers may not be as cheap and I'm not sure that they are necessarily cheaper than colour inkjets, but they are less hassle, particularly if they may be left unused for while.
I have a Hewlett Packard CP1515N, which prints well. The original toners lasted me 2 years, but I print a lot less than you. Replacing a full set of toners with original HP toner is not cheap, but buying remanufactured cartridges can bring the cost down considerably.
I think Epson and HP inkjets are designed to make it difficult to refill or use remanufactured cartridges. Brother and Canon printers have traditionally been easier to refill. I don't know if that's still true.
IJT Direct do some deals on Brother multifunction inkjet printers, which look like good value. £80, plus £7 delivery buys 5 sets of remanufactured cartridges and they throw in the printer for free. Reviews of IJT direct are mixed, but my experience of them has been fine, so far. At that price, it doesn't seem to be a big risk.
www.ijtdirect.co.uk/BroJ430
www.ijtdirect.co.uk/dcp195/
They also do some similar, but more expensive, deals on a Canon multifunction inkjet printer and a Dell colour laser printer.
www.ijtdirect.co.uk/mg5350/
www.ijtdirect.co.uk/dell1350rp/