I agree but it could have been done better, and since we are on a internet forum in 2016 its far easier
- Technology was changing all the time, and getting more expensive with it - that means coming up with an accurate cost estimation for a fairly low-end warship similar to those you've built before (e.g. a Rothesay or a Blackwood) is feasible, but where the technology is very new as it was with the Sea Slug ships then you end up with beautifully written estimates based on dud data.
- The UK economy was in deep trouble, which mean that the budget was being continually cut: at some point you have to cut capability to match the new budget. In OTL that was the decision to cut the East of Suez role instead of the North Atlantic Escort role: the UK could afford to do one but not both, and decided that East of Suez was ultimately less important to UK security than the North Atlantic role was. Problem for this is that you haven't magically found more money, but are just diverting a bigger fraction of national wealth to the RN. That can only continue for so long, after which IMHO you're still going to find the East of Suez role going away - and the expensive new carriers with it, probably.
- The RN was limited more by manpower than by funding throughout the Cold War - any realistic timeline dealing with more spending for the RN has to deal with this. If you are building the CVA-01 ships you HAVE to scrap something else or otherwise they'll just spend their time swinging at anchor in mothballs.
I would Concentrate on keeping long term just sufficient programs,
- concentrate early on NA but have the ability to send a force out of area v second rate opposition.
- not develop as much technology and types of ship, ie one class of frigate, by buying in less vital parts hopefully in trade with others.
- develop technology so its easier to fit into ships and you can deal with changes, ie try not to have very long Sea Slug style mags that basically have the ship designed around them!
- try to sell as much equipment as possible, so try to build stuff that others will want at least to licences produce them selfless.
With hindsight the RN had a lot of advanced technology and systems that did work and did even sell well. It has also had relatively few really hard tests since 1945. It wasted a lot of money and effort by not planning better.