This isn’t the movies mate. It would take some massive balls of steel for the UK to wait to see where an inbound missile would land/exploded as it approached the UK - it will be considered extreme aggression and that would trigger a response. Likely from NATO as a whole.
We know he has nuclear weapons and we have no desire to have a conflict with Russia. It is far more likely that if he wanted to go nuclear it would be tactical and in Ukraine - and I don’t think it is that likely.
I hope the talks can bring an end to this, they need to be able to give Putin something he can sell - such as joint governance of the disputed eastern regions - not great but sometimes you have to be pragmatic. The west/NATO needs to look at their relationship with Russia and find common ground and work from there. Putin won’t last forever and doesn’t represent the Russian people, we just need to swallow deeply, hold our noses, smile sweetly at him and be nice once the fighting stops and an agreement that is acceptable to Ukraine is found. In the meantime we need to continue to support Ukraine and not pay any attention to Putins rantings, honestly if he wanted to make a nuclear strike he wouldn’t have broadcast it on TV - he sees the west as weak (or did until a couple of days ago) and it’s for the benefit of the flappers to try and create disunity.