Thankyou,
My husband was all for digging over the area (no mean feat!) but i guess that'd just make the ground easier for the girls to go deeper. Also, we would never find all the stuff the pigs might,however much we 'rooted'!
We will keep checking the ground, as the problem has only come up once or twice in the year that we've had the girls there isn't a lot of stuff.
thanks again!
Z