You'll need to get a credit licence first, I don't think you'll get one unless you have been trading for while. I used to use a company called cardsave and found them very competetive. The rate any company charges is taken by what you think you will put through cards per month - the more money you put through - the lower the rate - if you see what I mean!!!!!!!!!
http://www.cardsave.net. If you contact them, they will probably help you through getting a credit licence also. One thing I didn't realise that I would have to pay when I handed back the machine was that I would get charged. Whether this applies to other providers I don't know.