Sure but any time the building of CV01 & 02 were discussed a number of cruisers were also planned...by the 1970s this shifted to DDG , but the battle group has to be taken in account. In Pugh THE COST OF SEA POWER he notes the 1970 fleet as being two large carriers and two small-helicopter carriers plus 2 LPD, that left enough to operate 27 U-Boat + 6 DDG & 59 DD/FF.
After a DDG & 6 escorts per Carrier/Amphib , that leaves only 23 frigates for convoy escorts.
IIUC while there was talk about escort cruisers and the like the concrete plans were for 2 CVAs and 4 T82 DLGs, I don't think big helicopter-cruisers were factored into the inflated costs in the political wrangling that lead to the cancellation of the CVAs.
I think its important to keep in mind that the RAF operated the aircraft that the CVA01 and 02 would have used, so its not like the money has to be totally plucked from mid-air.
Also, I don't think that by 1970 convoy escort would be like the WW2 Atlantic convoys; constant shipping keeping Britain supplied with food and raw materials so she can fight a long war. It would be more like the Malta convoys; big naval operations to reinforce Europe from US and Canada, so there would be a smaller requirement for huge numbers of ASW escorts and a larger requirement for powerful covering forces.