I hear all your arguments , but the most sensible question so far is do we need large expensive offensive units and the answer is quite rightly NO for obvious reasons.
I hear on the naval grapevine that the mine hunters will soon be history due to cuts, well one mine in a channel and all ports will be closed, a cheap but very effective weapon the mine, probably took out more vessels than any other weapon and still doing so today.
This country relies on imports, we have virtually no merchant navy left, but a dozen small auxiliary carriers like in the last war is more useful than large destroyers with one small helicopter, which cannot leave a convoy and probably not keep up with a convoy of container vessels in mid ocean. Where as a aircraft patrols a large area with anti submarine helicopters will do more damage, than a type 45 can. Also the type 45's with the proposed new large carriers are to prohibitive in cost to risk in convoy duties. Look to the last two wars and you will see this is the area that the real major war of importance was carried out. Offensive warfare can only take place after the defensive is won.
Better still as Churchill once said talk talk was better than shoot shoot, so basically we need good politicians to keep us out of scrapes, cheaper all round. The yanks are now feeling the pinch, but there economy and defence budget makes ours look like a child's pocket money.
Yes we could save money and redirect to the coal face, but that is politically impossible. You would upset too many senior officers in nice comfortable billets, check to see how many there are above Lt Comdr in the RN and what they do, same applies to the other services and check on the bull which is called traditional practices.
As for Invincible, she was laid up early because of her poor condition and was not suitable for saling on.