Well according to Wikipedia the design of the Upholder class was started in the 70's and the Falkland experience re affirmed the usefulness of SSK's. So if you drop the SSK force you lose the money already invested in the Upholder program and lose an asset that was useful in the type of war you where having your own CTOL carriers would be useful.
If you scrap the Leander class early you have fewer general purpose warships to provide ASW escorts for your carriers, convoy escorts if WW3 breaks out, escorts for your amphibs etc.
With regards to the Invincible class I can't see the UK building CTOL carriers and keeping any of the invincibles around.
If you delay the Trident program then you need to spend more money to keep Polaris in service and my recollection was that in real life the UK kept Polaris going as long as they could. Dropping the SSBN program entirely is probably going to be needed to fund a viable CTOL force IMHO. Even then you are still faced with a manpower problem.
Wikipedia states the UK contribution to the Trident R&D was estimated to cost 5 Billion pounds in 1982 (total program cost of over 9 Billion Pounds)and the relevant agreement was signed in 1982 so this seems a reasonable POD.
The SSBN force seems to be a sacred cow for the UK and I can't see the UK dropping this during the cold war.
I agree that a independent nuclear deterrence is vital.
No discussion about that.
IMO, increase of defence budget was nescesarry.
About Leanders, tehy were not really usefull any more, except for patrols in most benign environments.
And Type 22 is in construction and Type 23 in planing. Leanders were manpower intensive, Type 23 has 50 sailors less. Type 22 is about the same in manpower, but is much better frigate. So quality for quantity.
I didn't understand that argument about usfulness of SSK?
I agree that they are usefull, but IMO 10 existing SSNs could do the trick. And 7 new Trafalgar class will come in service by 1991.
After all, after 1990 RN scrapped SSKs.
And yes, we loose money spent on designing of Upholder, but we don't build them, and that is a big saving.
Maybe UK get's some sort of credit from USA or some grace period, so that she has longer period for paying for Trident.