In 2024 Putin warned of "catastrophic consequences" for the UK if the UK supplied long range missile components to Ukraine. The specific targets mentioned were UK military bases both in the UK and abroad. He then went on Russian State TV and explicitly stated that he was taking about potential nuclear attacks.
It was also around this time that Medvedev suggested that any attempt by Western powers, obviously including the UK, to return Russia to it's 1991 borders would result in all-out nuclear attacks upon all significant targets in Western Europe and the USA. Essentially a threat to bring about armageddon if the west continued to thwart Russian efforts at territorial expansion.
It has escalated across 2026 with Putin's cabinet expressly denoting the UK as a "legitimate wartime target", and the Russian Foreign ministry accusing the UK of "playing with fire" and warning of strikes against installations involved in the supply chain of goods going to Ukraine.
This might not be coming directly from Putin's own mouth, but it's undoubtedly reflective of his own views and likely orchestrated directly by him, so it's as good as the man saying these things himself.
So no, it hasn't been "going on for months", it's been going on for years. It's nothing new, and yet there is still no indication that Putin has any intention whatsoever of following through on any of it.