Last year someone recommended starting off a few beans early on (about now or earlier) to plant out early to mid May, and then start the rest at 1st May, to be ready for 1st June planting out.
If there is a late frost the early beans will goners, but if not they'll provide an early start to the crop.
I agree with DD. Early planting does not necessarily = very early cropping
One year I went to quite a lot of bother to protect an early planted out row of runner beans.... I fixed plastic corrugated sheeting either side of a traditional apex run of bean poles. This was then topped of with fleece... the bean plants grew steadily and well despite some really heft cold nights.
My next planting out a few weeks later didn't need any protection as chance of frost had passed... I also removed the protection from the first batch.... growing sturdily they were.
First lot of beans planted out produced pickings no more than a few days ahead of the second lot of plants to go out. Only advantage to me was I could clear some space in the greenhouse --- oh, and boast to my neighbour that I had the first bean that year!!
![wink ;)](https://chat.allotment-garden.org/Smileys/green/wink.gif)
Things do catch up.... it all depends on temperatures and light I guess.... they can't grow that much quicker until the conditions are right no matter when they were planted out.