Hi James,
Personally, I'm not sure that if a task force had already set sail from Argentina, we'd be able to get reinforcements to the south Atlantic quickly enough to make a difference (I think this was one of the problems in 1982), so I'd be inclined to suggest that British Intelligence gets word that the Argentineans are assembling a task force so sends the reinforcements before it sets sail, causing the Argentineans to back down.
I think the other factor that might be important is the possibility of a Royal Navy Hunter Killer sub being active off the Falklands (I could imagine HM Government making sure the Argentines thought that one was present, even if it was a bluff...). That option is obviously much less likely (though not impossible) the longer the Twilight War goes on - when you mention the Argentine task force setting sail in August, which year are you referring to?
Finally, the nuclear genie is well and tryly out of the bottle by the end of 1997. Who knows whether HMG might nuke Buenos Aires if the Argentineans make a move after that time? (Or again, threaten to do so as a bluff...)
I also think that the Falkland Islanders would manage to remain fairly self sufficient during the Twilight War, and there would be little likelihood of them voluntarily establishing closer links with Argentina.
Also, the Falklands has come up here before....you might be interested in this thread...
http://forum.juhlin.com/showthread.p...ight=Falklands
Cheers
Dave