I think one Astute with a full loadout of Spearfish would sink the lot very quickly. There are SSNs and there are targets and Spearfish can seriously ruin your day. On the other side of the coin, I would have no problem in imagining that a war equipped CVF carrier battle group could strike the islands and the mainland at the same time and still leave a credible CAP to protect the fleet. Type 45 would turn the low level ops of 1982 into one way trips. The Argentines know it and this is why they are sabre rattling again while we are relatively weak.
Some additional reading
here.