SSBN - not a cat in hell's chance of THAT being chopped. Nothing to do with boys toys for the Navy or nobody to nuclear deter against. Simple - if we ditch SSBN, our glorious leadership loses its place on the UN Security Council. End of story. And President Blair and all of his successors are not about to give up that little nugget of power in the world, are they?
A simpler solution - take the MOD telephone directory (have you seen it? - it's about the size of a large yellow pages), rip out alternate pages and disestablish all those posts and make the imcumbents redundant. Probably wouldn't notice the difference and would save a fortune, even taking into account redundancy settlements.