The main problem I can see with this is that it assumes a period of heightened tensions preceding any outbreak of war, that might be the most probable case but the military can't rule out the idea of an attack coming out of the blue. I could well be mistaken but IIRC even during the Cuban Missile Crisis the RAF didn't go to having planes in the air like SAC's continuous airborne alert - the UK simply didn't have the number of personnel, aircraft, or financial resources to operate the ones they did in that manner. The highest readiness state they had was Quick Reaction Alert with aircraft being fuelled and armed, sitting on the hardstand next to the runway, with the crew either onboard or in a caravan right next to it.
I'm not sure even something like the Titan II would be enough for the UK to operate under a launch on warning system. Unlike the US due to geography the UK would only get four or five minutes warning of incoming missile from Eastern Europe or the Soviet Union proper, that pushes the decision-making time down so low that it raises the prospect of launches being made due to false reports of an attack as there's little time for rechecking or confirmation. Any British silo-based missiles would most likely be retaliation weapons to 'ride out' the initial attacks and then respond in kind, at least for the fifteen or so years they'd be operational before the CEP of Soviet missiles improved enough as to make them redundant.