beans

It's still only March - much too early IMO

Sow seeds in greenhouse late April and plant early/mid May (after your last frosts) in a normal year, this year we have a cold Spring, so think sowings will all be a week or 2 later.

Way to early to even think about sowing runner, dwarf/climbing/french beans.

Wait till second week of April at minimum to sow in greenhouse or under cover for dwarf/climbing/french beans to plant out in early May or sow direct in the ground early May.
For runners, sow in greenhouse or under cover end April to plant out around 20th May
Sow in ground around mid May too.

Agree with everyone else here. Wouldn't dream of sowing them under cover until mid-April and then they would only go outside after the last frost. Besides, beans are such rapid growers, they hardly need the head start.
As an aside I did read once that Runner beans are technically bi-annuals, so if you can pot up the roots and keep them warm over winter, they'll crop a little earlier the next year. Can't find where I saw that though and it's obviously not really worth bothering with as it's such an easy crop to grow.

Many years ago I grew my runner beans up a wigwam, and being a bit short of dalek space at the time I just dumped all my garden waste on top of where they'd been growing that summer.

When I got round to shifting it the following spring I was surprised to find lots of new bean shoots, mostly at least 2 or 3 from each original plant. Only reasons I didn't continue with the experiment was that I'd planned to grow them in rows that year, and also with my light soil I wanted to get plenty of organic material underneath the next crop.

Having once been very nearly caught out by a late frost in early June, I never plan to plant mine outside until then, which means sowing indoors in early May, although I do sow some directly as well to extend the cropping season.