The message
from Rick McGreal contains these words:

Someone mentioned a way to gather worms....

Something about a plastic sheet after rain?

You've reminded me of something an American told me elsewhere on
usenet,which I meant to try at home but forgot. She used a worm stick to
fetch them to the surface. IIRC correctly the worm stick is something
like an old broomhandle, sharpened to a point at one end and notched
down one side at about 2 cm intervals. Jam the point in the ground, and
run another stick up and down the notches to vibrate it. Let me know how
you get on :-)

Failing that, beg a sackful of old horsemanure from a local
stable..some I acquired a while back and am only just putting to use,
contain thousands of worms which must have been breeding in the luxury
conditions.

Janet.