An important thing to keep in mind is that when the task force was initially sent, there was hardly any certainty as to what was going to happen. At first it was mostly a political move, firstly to coerce Argentina into leaving the islands and secondly to placate those in Parliament and the general public who demanded action from the Thacher administration. Many believed or expected that the task force would be turned around mid-voyage with whole crisis blowing over. At the same time, there was understanding among many in the military that there was certainly a risk of conflict. As time went by, the military planning process became more decisive and more specific as political options steadily evaporated. So the military's outlook upon the situation changed over time, and also there were different individuals with different opinions so it's hard to judge overall opinion.

As the British task force staged at Ascension Island in early April they were planning for a number of different options under the orders of the war cabinet. At first no one knew what would happen at all. At an early meeting of naval captains, most were "eager to show what their ships could do, but believing that, after some sort of armed demonstration, perhaps a skirmish with the Argentine navy, the enemy would make terms" (The Battle for the Falklands, Hastings and Jenkins). They were worried about the air threat, but nevertheless most of them later admitted after the war that they had significantly underestimated the capabilities of the Argentine air force. As for the land campaign, Woodward's staff figured that once the landing force was safely ashore then the campaign would basically succeed, so they didn't put too much stress or planning effort into that side of the equation. At the time, they took the surface warship threat seriously because the Argentines were equipped with many of the same systems as the British (such as the Exocet). Admiral Woodward radiated confidence about the overall operation and there was plenty of eagerness to go around but many in the Navy, including both enlisted men and high ranking officers, had strong doubts. Admiral Fieldhouse wanted others to realize that it was going to be "the most difficult thing we have attempted since the Second World War." This was in April however. As time went by, the Navy lost much of its optimism, especially after they started losing ships.

Overall, the Navy definitely had mixed feelings about their chances but they generally underestimated both the Argentine military capabilities and the Argentine political resolve to fight. In reality the conflict was very close and it took awhile for the British to realize just how much damage the Argentines were capable of doing to the British fleet. Source for all this is The Battle for the Falklands which is a great read and, afaik, the quintessential history of the war.

I'd love it if someone could refute / prove this It's basically a Ricky Gervaise joke saying that British ships at the time had a longer range than Argentine ships and so the war was similar to a grown man holding a midget at arms length and kicking him in the bollocks, I'm sure that analogy doesn't reflect reality but how close is it?

Not an answer, but I'm on mobile at the moment and having trouble finding it. Could you pop in a link to the previous Falklands discussion? I'd be interested in reading it