Sandy writes
Ahhhh that explains why I lost some of my seedlings (hollyhocks,
rocket, geraniums) recently, having sprinkled them over the surface of
a largeish 12" pot. They got to about 2cm tall then just fell over and
died!

I'd have thought they'd be OK. It's the having large areas of empty soil
which seems to be a problem. At 2cm are you sure you didn't get damping
off (which despite it's name is fungal) - did the lower stem get thin
and spindly?

I've just sown pak choi seeds in a similar manner and they've all
germinated ok but are currently at that same "delicate" stage so maybe
I should hold of watering them a while. Surface soil is dry but feels
moist below.

I wouldn't. Their roots will be tiny and won't be able to reach down
into the moist soil if you let too much of the top soil dry out. Keep it
all moist.

--
Kay