Not being funny pal but what you have is probably 1 in 1000, and i still wouldnt breed off them because the pups almost certainly wont work. KC terriers have been bred for looks for too long and have lost the ability to do proper earthwork in all but a few cases.
And your second comment any dog thats trained right will go down a hole...is true, but its what the dog meets down the hole that splits the difference. Any numpty can run an empty earth, i doubt it if your dogs will stick it in the long run, but i really hope they do. And well done for trying and giving it a go
FTB
Just because