The Victorious' rebuild would probably have lasted 20 years, taking her to 1980 or so, not very long if you buy her in 1969. The Hermes and Centaur were fitted with steam catapults, the Bulwark and Albion were only fitted with hydraulic cats. Which is probably why they were turned into commando carriers in the late 50s, it being crunch time to refit with steam cats or do something else.
Just a word on the money available between 1967 and 1973. The British govt spent 30 million Phantomising the Ark Royal, 13 million making Tiger into a helo cruiser and 25 million making Hermes into a commando carrier. I struggle to believe that 68 million pounds would not have been better spent building 80% of CVA01. Its the same story with TSR2, after cancelling it on the verge of production after spending 195 million, they spent 46 million on F111K only to cancel that too then buying the F4M, developing the Jaguar, buying extra Buccaneers and developing Tornado.
The turbojet powered blue steel mk 2 could have kept the V force viable until 1975 or so, long enough to build the first 3 polaris (posiden) subs after a later start.
From hindsight it looks bad but you need to look at things from the perspective of the 1960's and 70's.
I am just about old enough to remember the 70's and back then it was agreed that Britain was finished as a world power and only the USA and USSR counted for anything.
Britain having carriers or not having them MADE NO DIFFERENCE to anyone except those trying to keep their jobs in the defence industry.
The consensus was that any war beyond SAS actions would involve a Third World War with the USSR. The conventional superiority of the Warsaw Pact was so great that NATO would have to go nuclear in days.
What's the use of a carrier, cruiser, extra 500 Chieftan tanks, TSR2 if the bombs start falling after 2-3 days tops?
Another big problem and one which continues is that the cost of almost every major weapons project spiralled out of control.
F 35 anyone?
TSR2 was already expensive and there were no guarrantees it wouldn't cost far more before being ready for service. The British bought the F 111 to keep the airforce happy and because they needed American help to support the value of Sterling.
Denis Healy wanted to cancel Concorde too.
Almost every modernization and rebuild cost far more than originally budgeted so yes they could have spent the money better but unless you had Dr Who's TARDIS there was no way for them to know that.