What do people in the UK think about Putin's threats to destroy Britain with nuclear missiles and to sink the British Isles?

Anyone that launches a nuke on any other country will themselves have every nuclear equipped nation firing nukes at them in turn. You do NOT use nukes unless you want to die. That is why it is called mutually assured destruction. Only someone who is suicidal/homicidal would do this. And we have to consider the possibility that putin is both those.

As realistic as his “special military exercise” winning in the Ukraine.

It’s all piss and wind.

Bravado.

It’s a worry with a nutcase having his finger on the button