In terms of overall value for money, there was a review in the past about the cost of 3 options, sub-surface, surface, land based and air. Unsurprisingly, the sub-surface option was the cheapest and - in my opinion - the most flexible and the optimum solution for a deterrent.
CASD is a must, otherwise what's the point. If the UK was involved in a scenario in which there were *really* high tensions, I can't help but believe it would not be beneficial if it was published a UK SSBN just put to sea either. It would signal an intent to escalate.
I'm glad I read that review, from what i've read so far it's not packed with BS trying to bluff it's way through as fact.. It's accepted that cruise missiles cannot give the same level of deterrence and security that current SLBMs can, it's accepted that developing the warheads for cruise missiles/free fall bombs adds a high amount of technical,
financial* and shedule risk (critical challenge was thrown in too) to the program which is futher extrapolated later on. Things like development for a cruise missile/FFB warhead something like £8-10bn compared to £4bn for a ballistic missile.
It's also quite good to read that they accept that if any alternatives were to be developed, a fleet of 2 successor SSBNs would still be required anyway to bridge the gap of the Vanguards leaving and the successors coming in.
Overall, this review has been very helpful to the nuclear deterrent IMO (but i'm still reading). The technical and financial comparisons have shown that the methods we're doing now are the most capable and the cheapest, the only
real issue Trident can be picked on is the concept of nuclear weapons as a whole. The issue with cruise missiles and posture is more political, but the financial implicaitons - which realistically is the driver of this review - puts that idea down.
The costs of delivering an alternative system could theoretically have been cheaper than procuring a like-for-like renewal of Trident were it not for timing and the fact that the UKdeterrent infrastructure is finely tuned to support a submarine-
based Trident system. Inparticular, the time it would take to develop a new warhead (itself a costly and high riskexercise) is judged to be longer than the current Vanguard-class submarines can safely be operated. Bridging the resulting gap in deterrence capability would involve procuring two Successor SSBNs so that a Trident-based deterrent remains available until at least 2040. Doing that at the same time as investing in the development of a new warhead, new missile, new
platform and new infrastructure means that transitioning to any of the realistic alternative systems is now more expensive than a 3 or 4 -boat Successor SSBN fleet.
*i.e the entire reason for the bloody review.
Although a 4 boat fleet is cheaper apparently (than a new system), be prepared for a 3 boat fleet. Personally that is what I am expecting to happen as much as I would like to see a 4 boat fleet.
EDIT: Update on HMS Queen Elizabeth with some nice arial shots showing the ship with both her islands on.
https://navynews.co.uk/archive/news/item/8365
She has only got two sponson sections to be added and the ski jump, the ski jump itself consisting of 5 pieces (+ the lifts*). The ship will be structurally complete in October this year with the rest of the work being fitting out internally. Painting is ongoing with the bulbous bow being primed with red and being given an undercoat of the creamy colour the islands were in.
The ship overall will require 5 coatings of paint, which is 1.5mn square metres of paintwork to be done. Then there's the special deck coatings for the flight deck.
Highly impressed by her progress, won't be long until we've got this ship alongside in Rosyth being fitted out and we see Prince of Wales coming together incredibly quickly, quicker than Queen Elizabeth that's for sure because the sections will have a higher level of quality of the fitting out.
Normally quickly followed by the greenies degaussing the TV's on the ship as well, they had a tendency to go a little green over time 
