Re the Salisbury Poisonings, I hope that Sergei and Yulia, wherever they have been relocated, are a bit more careful re security. He can't have been the sharpest of spies to have kept his original name, not to even have a burglar alarm fitted to his house, and to have photos of himself in his house wearing all his Soviet medals.
(I know an alarm would not have stopped Novichok being applied to the front door but still, it's the basic level of security for most people, let alone spies who have been double agents)