I have done alot of research into card payments as I have just started renting a room.
FSB has a good deal with Streamline, but to use their co-op business account you would need to be a member ongoing. If you want to be a member every year then it would work for you.
FPB has a the deal with HSBC and has NO MINIMUM CONTRACT, you can cancel through FPB at any time. The rates are good (better than streamline) and also you get first 3 months rental free.
Check out this link
Card processing | Mobile card terminals
I signed up with Abbey for a business account. Free charges forever.