Re: Err - Why not get it back in the air?
"Would it not be better to reunite it with its three previous colleagues and an airframe and fly the bugger about?"
Well it would from our point of view, and indeed many other historic aircraft too, but that would require Type Certification by the CAA. When BA and AF withdrew their aircraft, Airbus (as the certificate holder at the time) handed it back to the CAA, and without that certificate the aircraft can't fly.
To keep the certificate is a lot of work, and requires makers of airframe and engines, and maintainers to keep the certificate up to date through service bulletins, updates for any mods (eg new parts as the old ones become unavailable), and to support with necessary spares. All of that's very expensive for complex jets, especially since OEM spares are rarely available, and have to be substituted and relevant supplementary certificates prepared and approved, along with all the documentation.
Similar reason for the remaining Vulcans and Victors etc ceasing to fly, although as ex-military aircraft they don't have a TC, but need a Permit to Fly backed by airworthiness support from the makers or organisations of similar standing. There was a lot of trouble when a retired Victor briefly became airborne during a fast taxi run at Bruntingthorpe a good few years back, as it didn't have the requisite approvals. For simpler aircraft, they still require a Permit to Fly, but it's a lot easier to get and keep that for those for smaller or lower tech aircraft than for Concorde or the like.