Think Tanker
I've only had a chance to skim read the paper but a couple of things spring to mind:
1. F-35C is the carrier variant and is probe and drogue refuelled so no need to add the cost of converting Voyager to boom refuelling, which is just as well as
2. You have understimated the costs for providing a new long-range MPA. Once training systems, additional new build facilities, maintenance and crews for your MPA you would need to at least double your costs, and maybe treble them. Particularly if you wanted the UK to remain a 1st world player in the ASW/ASuW business.
Like others on here, I think the biggest flaw in the paper is the assumption that anything "saved" by cancelling successor would be reinvested in the rest of Defence. It won't be, it will be spent on the sacred cow that is the NHS, or on education, or on keeping the feckless, lame and lazy in benefits.