Is the physical terminal important to you, or do you just need to take payments by debit/credit card?
Sign up for a Paypal business account (free), and upgrade to their "Virtual Terminal" product (£20/month) and you get a card processor that can run in any PC browser screen. You just type in the card details rather than putting the card in a machine. Ideal if you've got an online PC and you aren't doing volume sales.