"Can someone elucidate as to why Vulcan carried on so long and Victor didn't? The discussion passed me by at the time. What was wrong with Victor?"
I'm not an expert by any means, but according to Vulcan 607, it was the change from high attitude to low attitude to avoid Soviet air defences. This placed more strain on the airframes, chiefly the wings, and reduced their service lives. The Valiant was the most severly affected apparently, followed by the Victor and then the Vulcan (the rigid wing supposedly coped better). Hence the Valiant was retired pretty quickly and the Victors were converted to tankers, leaving the Vulcans.
I'm sure someone who actually has first hand knowledge will be able to provide a better answer though.