Here’s my own special conspiracy theory for you:
Retaining the Falklands has cost the UK and the world untold billions. My belief is that we signed a secret agreement with the US which means that we would support them militarily whenever requested, in order to get their logistic and satellite support during the Falklands war. Initially the US was strongly on the Argentinian side, with (?) Madeleine Albright making very anti-British noises, but something happened for them to switch.
Since then, we have become US poodles. Before 1982, our support for US foreign policy was lukewarm – we stayed out of Vietnam, did not provide much in Korea, etc.
Whey else would we keep Trident, or have gone into Iraq?
I’ve had this hypothesis semi-confirmed three times, once by a security man who was attached to a junior minister of defence, once it was hinted at by a very senior civil servant from the MoD, and once by a high-ranking UK officer who spent time seconded to the Pentagon.