I don't think killing grey squirrel and minks is a good idea
Grey Squirrels? Most certainly YES, they're nothing but bushy-tailed rats.
I understand they're officially classed as non-native vermin in the UK, so if you should be unfortunate enough to catch one, it's actually illegal to let it go.
i don't think it's right to kill them. If you want to see red squirrels go to the Isle of Wight.