In message , David in
Normandy writes
Stewart Robert Hinsley says...
Many plants flower once and then die, including annuals and biennials.

Would it be worth while collecting any seeds from a gone-
to-seed bamboo and sowing them? Do they need any special
climate or care to germinate?

He'd either succeed or he wouldn't. Advice on germinating bamboo can be
found on the internet, but in addition to the usual caveats about
believing everything you read on the internet, any advice found may not
apply to all species.

I saw a huge bamboo clump at some famous country house on
TV that was supposedly very old (may have been 50+ years
but I can't remember) and the head gardener was quite sad
because the clump was flowering and he would lose the lot.

Would any young runners from the parent bamboo also die?

Some supposedly monocarpic plants (e.g. Agave, Yucca) also reproduce
vegetatively, but the stereotype of the gregariously monocarpic bamboos
is that the whole clump dies. The real life answer may well be that it
depends on the species.
--
Stewart Robert Hinsley