A butter bean is a haricot (or Kentucky) bean

Hello.
I get mine from the supermarket, dried. They are the largest/fattest of the dried packet beans you can buy, at least where i live they are. We've just enjoyed some this evening in a steak & kiddley pie.
As for growing them, why not just try?
I imagine you'll have more luck next Spring though, as plants grown indoors now prob won't do well, or not well enough to produce their own beans.
Runner beans are not frost hardy are they, so praps try planting some (if they are viable - is that the word?) in pots indoors in March/April then put in the ground after frosts have gone? What does anyone else think?
Good luck.