The reason that the nuclear deterrent is carried in submarines is so that the UK has a credible second strike capability. It's no good having all your nasty nukes strapped to shiny aircraft that have just had their runway bombed.
Do we also believe that any cost saving will be reploughed in to Defence plc's coffers? Methinks not somehow..
Deterrence is a funny old game but better to be on the train pi$$ing on to the platform than running along the platform trying to pi$$ in the train....