lots of flowers on runner beans but very few beans

Don't know where in the UK you are but according to RHS - Warm temperatures, especially at night, may inhibit bean formation by preventing pollen grains from germinating. Cropping should resume when cool nights return in September.

Someone always asks this every year, as runner beans take a while to start setting beans. If it's dry as Wagger says, it makes the beans less likely to form. Runners love lots of water and coolish conditions. In France almost no-one grows them, except as an 'ornamental' plant, so you only find the seeds in the flower section not under vegetables! We've tried them for six years and except for last summer which was very wet, have been unsuccessful in getting many beans. So we grow climbing French beans instead.

I think it's a bit early to be expecting your beans - more of the flower stage definitely here...