"Our fleet was not plundering, it was fishing sustainably in international waters which Iceland suddenly claimed as its own"

That's not how the Icelandic government saw it. Nor, eventually, the way Nato and the UN saw it, who both backed Iceland's position on their declared fishing limits (as did, for reasons of national security, the US). I remember very well how we all cheered when the Icelandic gunboats tried to ram our trawlers and our crews' superb seamanship won the day - "That'll teach those rotten foreigners a lesson!". But the U.K. eventually had to accept the 50-nm, and subsequently 200-nm, limits.

Iceland was acting to preserve its own fishing industry, which played a far, far larger part in their economy than ours has done in the UK economy, and the UK was the interloper and, as far as Iceland was concerned, the aggressor. As I said earlier, it's very amusing to see how different people's reactions are when the boot's on the other foot.