Not sown any yet I usually leave them until the first week in May.
I've read, somewhere, that Runner beans are more sensitive to weather than French beans. Actually, Runners are more demanding in lots of ways - flowers need fertilisation and they cross with other beans. Need warmer nights.....I prefer to eat CFBs too - not as coarse skinned as RBs - which are probably better for drying.
I find if I start too early they get to leggy in the GH . So I don't start any outdoor beans until the first week of May? Chit in tubs and pot on, usually plant out 3rd week of May.... they don't like cold winds
I planted my beans about 20th April. 3 lots in seed trays. Soissons, climbing french for drying, 30 in tray, Dwarf french for drying 2 trays, probably 60 in each and a round podded french for eating fresh/freezing about 60 in one tray.
Not sure I'll keep growing the climbing one as it is a lot more work, though the yield is higher for the land. Also, they mature a lot later than the dwarf ones. Then in the kitchen, they tend to need a bit longer cooking to soften up.
The benefits of growing for drying are: cheap to store and a good source of protein. Also once you have found ones you like, you just need to keep back as many seeds as you want the following year so never need to buy them again.
I planted some DFB seeds in modules yesterday they were a bit out of date but worth taking a punt. Sat them on moist compost the covered with some loose compost to prevent them drying out.
I love beans but I haven't sowed many yet, and the ones I did haven't made an appearence yet. I can't wait to direct sow
Started hardening off my first batch of slenderette & roquencourt today.