Can I use this year's runner beans for next year's plants?

Roseberry, it is good that you left the beans on the plants to dry off. Yes, they should do well as seed for next year. Leave them on the plants for as long as you dare then take them into the shed and let them finish drying off completely. Then just store in a paper bag in the fridge until you need them - provided that you havn't already put them in a casserol!

i have not bought beans for about 6yrs now, just keep drying them and keep in the cool coalhouse ready to use in march. plants for free and great.

I always grow my runners from seeds saved the previous year, BUT they may eventually deteriorate somewhat. Keep and eye on this and use fresh stock if you notice deterioration.
You can do the same with broad beans also french beans. With all of these you will find the plants adapt slightly to suit your soil and conditions,. Can't be bad!