Although highly expensive the UKs SLBM deterrent is the only option really. It provides that strategic to tactical nuke option {dial a yield) all from one platform.
Sure it does-but the question is that platform will rarely,if ever be used & it’s (atleast officially) not used for anything else.I was thinking more along the lines of deploying cruise misiles on the Astutes & aircraft along with a stock of air-launch bombs.Those platforms won’t be invulnerable,but the costs should be far lower.