Its been done to death over the last few years. Fundamentally the UK is not ideally suited for sustaining a credible airborne deterrent in the current threat environment.
We'd need lots more aircraft, lots more dispersal airfields, a whole new nuclear device to drop, a significant expansion in the RAF to ensure that sufficient aircrew are available to crew the squadrons on the nuclear strike role and also meet our day to day commitments, and also a wider uplift in manning and real estate.
Or we could just build 4 submarines, crack on with it like we've been doing for 47 years and be done with it...
(I know RELENTLESS is a bit more than 4 SSBN but its still a damn sight less than V Force Redux).