You sound just like i did about a year ago when i made my first e-comm site! hehe
Firstly, i can't re-iterate how much you have to be willing to spend a bit of money. Use something like worldpay or netbanx as teh merchant, or check what bank the butcher is with for his credit card machine (PDQ machine) and get him to ring them and see who they recommend. If its natwest - they use worldpay.
It might seem like an expensive option, but then you don't have to worry about the secure side of things. If you are gonna do it yourself, you're gonna need a SSL certificate which can cost quite a bit (www.verisign.com
for more info i believe). Also, emailing the results will only be secure if encrypted using something like PGP (or GPG!) but we're talking some serious stuff here.
Remember that if credit card fraud takes place, you the website designer is held responsible if the correct security safey measures were not set in place by yourself. Hence, i always use worldpay or netbanx (www.netbanx.com
Hope this has helped you out a little, feel free to post any more qns you have