It may have been a matter of who in the UK was doing the expecting. As Admiral Woodwards' book "One Hundred Days" observed, "There were several entirely competent organisations who felt this was a doomed operation, to include the Army, the RAF and the US Navy"

The typical Brit on the street may well have considered the Argentinians to be a second-rate opponent, but from my various readings, I never got the impression that the professional British forces actually going to the fight considered the Argentinians to be anything other than dangerous opponents, especially given their 'home turf advantages'. If anything, the fight was concluded with fewer losses than they expected.

The anti-ship missile as a concept, of course, was not new to the British. The Soviet navy were the pre-eminent users of the things, and the exact force that the Royal Navy was expecting to go up against. As a result, the idea of the early warning picket, such as Sheffield was performing when she was struck, was already something which was done. (And in fact the concept dates back to WW2, when US Navy destroyers would be out alone as pickets to warn of kamikaze strikes, at the risk of becoming a loss because of one).

One modification with the arrival of the Sea Wolf Leanders and the Type 22 frigates was the use of the 'goalkeeper', the Type-22s being kept around vulnerable targets specifically do deal with the sea-skimmers which the Sea Dart on Type 42 and Invincible had difficulty with. This became known as the Type 64 destroyer, a Type 42 providing the Area air defense and warning, with the Type 22 providing the anti-Exocet point defense. Unfortunately, it also wasn't guaranteed to work: Coventry was sunk as part of the Type 64 destroyer by old-fashioned iron bombs from 'planes due to a bit of bad luck and maneuvering, which likely would have had the same effect against an exocet attack.

It is also to be pointed out that despite the pubicity, it wasn't the missiles which sank most of the British ships. Exocet was responsible only for Sheffield and Atlantic Conveyor, and damage to Glamorgan. Ardent, Antelope, Coventry, and Sir Galahad were lost to dumb bombs, and one of the Leanders (Plymouth or Yarmouth, I can't recall) had a lucky escape when a wiring issue aboard an Argentine sub resulted in a dud torpedo, not to mention a number of ships hit by bombs which failed to detonate.

After the fact, some lessons were learned as well. One, as Wanderjar observes, was the importance of the CIWS. The other was the requirement for an airborne early warning system, this led to the development of the Sea King AEW, with the searchwater radar.

Follow up question regarding naval losses. Is it true that the British modified their naval tactics with the Exocet anti-ship missile in mind? To my knowledge, this quite advanced missile was a cause for naval damage and losses.

Here's another one; why did the argentine navy stay in port? What real danger did they pose after the sinking of the belgrano?

Follow up, any highly recommended books on the subject?