I cannot recommend a particular Brand, but can I recommend going down the Laser Route.
I'm my opinion the added cost of the ability to put a small flash of colour onto an invoice, far outweighs the small extra cost of a Colour Laser Machine and improves the image of your Company out of all proportion.
It also saves you the cost of having Headed Notepaper for all your other Correspondence.
I have a Samsung CLP325. It's mainly used for printing Time Sheets, which do not run if they get wet.
Many people get extremely excised about the cost per page and will buy Machine A rather than Machine B because of a 0.1p in the printing cost. That's not even the cost of a Mars Bar each day
Buy from a company that is able to put your machine back in working order - Fast. £20 or £30 of purchase price and 1p per page print cost are as nothing to the trauma caused by not being able to print your invoices for 48 hours.