I think several things will dictate any response to Putin using nuclear weaponry.
First, where he targets- if he hits any NATO members, he’ll be getting a warm reply.
If he targets one of the “hoping to be NATO” countries, the response will be the same.
Added to that, where, within any country he targets, will play a large part in the response.
If he targets a town or city, goodbye world it’s been a wild ride.
If he targets a strategic military site, say for example Brizlee Hill in Northumberland, I think a like for like nuclear response, and also a bunker busting “Goodbye Vlad” missile to take him out will be sufficient- he must be taken out, but whoever steps in after him needs to see we aren’t fucking about but are still open to de-escalation.
It’s a terrifying thought, particularly when we have a current leader who idolises another fucking psychopath, but if handled correctly, even a strike on NATO soil needn’t be the end of us all.
I’m still holding on to the diminishing hope that his nuclear arsenal is in a similar state to the rest of his military, and he’s playing the biggest game of bluff ever, or if he launches, it just goes boom at the launch site.