Hi there,
I have been using a card reader from payleven. It is portable and robust that works through your mobile phone. Personally found it great, a very easy method of being able to allow my customers to take card especially as I can take it on the job instead of waiting around for payment after. I got mine for £58.99 in Plumbfix with a 2.75% per a transaction. They have a customer service that I rang up before buying the device just to ask a few questions and found very helpful and friendly.
I've recommended it all ready to a few of my mates and would to you to!
Alan - Plumbing Locals