Hi Ferg.
I once used those CK you mention from toolstation(they could of improved the mechanism or material)
I found them to sometimes strip the inner cores whilst taking the outer sheath off. Exposing copper!(and yes they were adjusted properly)
Not everytime but sometimes this would happen. Then in the end I think the cast jaw just broke whilst stripping some 1.5 twin.
Just a heads up but for 14quid they could be worth a go for yourself.
To be fair the first time they did that it would have worked out cheaper to buy a better and or different pair.
Thanks.