Mike Lyle wrote:

I'd dig them all up and replant the best ones four inches apart.

Thanks Mike, must admit this was my gut instinct

The
soil is probably very fertile, as you've been so generous with feeding,
so I wouldn't do anything at root level.

Thought I might just take the opportunity to give it a really good dig
over once the bulbs are out of the way, as it's not been done for the
last 20+ years...

But I wouldn't do it till the
leaves have died down in the usual way.

Right - that was another thing I was wondering about - whether it'd be
best to wait till they've died back, or to do the sort out now, and
replant the best with plenty of room to grow now - I know some folk do
lift their daffs and replant them elsewhere while the foliage dies, so
that they can get on with replanting the border. Or will they have done
all the growing they're going to this year?

Jan