Perhaps I am a bit naive here....but sending the entire fleet of Vulcans to the mainland would have been just a bit more difficult. Where was the support package to come from as surely the Argies would have been just a bit more of a problem at home than they would have been at Port Stanley.
It was a stretch to do the Black Buck strikes as limited as they were....someone explain to me the assets that were in place/available and ready....for going to the mainland and survive to fight another day/night?