Now I'm going to contradict everyone here (as is my wont)
. My understanding is that only the late production Vulcan B.2s that were fitted during their production with wing hardpoints for the cancelled Skybolt were designated Vulcan B.2A. These hardpoints were only resurrected to carry Shrike missiles for the Falklands War.
As far as I know (and I do stand to be corrected here), eventually most of, if not all Mark 2 Vulcans were retro-fitted with the Olympus 301 and most, if not all could carry Blue Steel.
MDLB