I have successfully germinated these seeds following the advice on the
seed packet (two weeks on in a warm light place, followed by two weeks
in the refridgerator). The packet then says to remove seedlings "as
they emerge" and pot on.

I read that as "take the seedlings singly from the pot as you see them".
I have about a dozen showing, no more than a couple of millimetres tall.
Is there a reason for this very specific advice to remove as they emerge
and would it do any harm to let them grow on together to a reasonable
size before pricking out? The packet does indicate that they are
difficult to germinate (but offers a promise that by following their
specific instructions one would be successful - is it perhaps because
they normally germinate at very different rates and the percentage of
such germination is low?)

I really don't want to loose them so any advice would be much appreciated.

Thanks

(East Yorkshire)