You'd not be lucky to get ferrets like that, it's probably the easiest ferret to get hold of, one that comes away and does not stick with the job till the end.
The roots on a hedgerow are a bind but not as bad as around big trees.
Lessen your chances of digging by getting a couple of jills, the smaller they are, the more chance the rabbits have of getting away.
If it's in range on an old 8ft finder then i would not find it a major worry if things go tits up.
By the way, are the escapee's still around CB?
Dig the shortest route in possible, sometimes it's easier to tunnel in sideways a