Thanks Paul, good analysis.
My suspicion was that the F-4K was always intended as a one for one replacement for the Sea Vixen on all in service RN carriers, bar Centaur, from the mid 60s with or without the introduction of the CVA-01 design and that the reason it didn't happen were political.
The official line was that the Phantom was too large for any RN carrier but Ark most modernisation and that the original plans were unrealistic. The fact Eagle cross decked USN Phantoms disproves this, as does the RAN enquiries into operating F-4Js from an Essex (or possibly even a modernised Centaur) and I wondered then if the claims that the F-4K was incapable of doing precisely what it was designed to do (i.e. the extra thrust, extended nose wheel etc.) were nothing more than disinformation to justify a political / financial decision to run down the carrier fleet.
I imagine the last thing politicians wanted was for a future government to be able to easily reverse their decision on a carrier replacement in a decade or so because Phantoms were successfully operating from modernised Eagle, Ark, Victorious and Hermes. The UK does seem to employ a scorched earth process upon cancelling defence projects, where the US has large reserve fleets and aircraft bone yards etc. since the 50s the UK has pretty much sold, destroyed or made unusable any platform to ensure it can not be brought back into service following the decision to retire / cancel has been made.
This makes for an interesting wiff, potentially not only could Victorious and Hermes been upgraded to operate Phantom, but so could Centaur. Ark and Eagle could have been strike carriers with Bucaneers as well as Phantoms while the smaller ships could have been CVS with upgraded Gannets serving along side Phantoms into the 80s. All of this could possibly have been at a lower overall cost than the acquisition of the Invincibles, conversion of the Tigers, purchase of additional Sea Kings, and increasing the number of Seadart armed air defence ships. A very different RN could have began intoducing a class of smaller (than Ark/ Eagle, larger than Hermes) CTOL carrier in the 80s, designed specifically to operate Phantom and then convert to a navalised Tornado (or F/A-18 for the cynical) and maybe even a Gannet replacement. Air defence ships would have been fewer in number but more capable, i.e. additional improved Bristols and the Type 43 and with the air umbrela and strike capability provided by the carriers the Type 23 Frigates could have been smaller, cheaper and less sophisticated.