"Mike Lyle" wrote

In a moment of mindlessness I started runner beans far too early. They
are now, of course, far too big, and can't be planted out till the end
of the month.

If I pinch out the tops, will the resulting side shoots develop into
tall twiners, or will the plants simply remain bushy?

Well seeing as a lot of the allotment holders on our site (the newer ones!)
have had their runners planted out for a couple of weeks why not give it a
go yourself. As a backup, in case of frost, plant some more now, some of the
older gardeners planted a few beans every few weeks to get a constant crop
over a long time and it worked.

--
Regards
Bob Hobden
W.of London. UK