Wot Gordon said. These birds haven't flown, haven't even been aeroplanes, for over a decade. They are museum artefacts decomissioned with no thought to recommisioning and no moth balling. There are no spares, no drawings, no specialist tools etc etc. You would have to re-certify these artifacts, and all their highly complex 1960s technology systems. And you'd need Airbus on board (no chance), a TC (no chance), and a C of A (no chance). And none are for sale.
If you believe Branson could have kept it flying, you probably also believe in the Easter Bunny. Smart marketing guy, old beardie. Half the population or more of UK think he could have saved it but for wicked old BA and AF saying "NON". Yeah!
It would probably be cheaper and easier to design a build a modern replacement supersonic airliner than to get a Concorde flying again.
And anyway, she was a bird of her time, a bird of an age when what could be done was done (like sending men to the Moon and bringing them back). She is not a creature of the safety-obsessed accountant-driven unadventurous 21st century. Remember her for the glorious aeroplane she was and rejoice that we had her for almost 3 magnificent Mach 2 decades.