My understanding was that BA wouldn't sell it as Mr Branson wanted to fly charter/scheduled to the US. However the premium market, which Concorde commanded, BA wanted to transfer to their normal 747/777 fleet. If they had sold the aircraft to him that would have put that revenue stream at risk.
Which is why the remaining BA concordes were given away and /or allowed to rot by removing fluids from the aircaft. I understand the Air France is the best preserved example as in theorey has had hydraulic/electric power supplied on a regular basis which preserves the seals on the systems.
There is a thread on another avaiation forum about the possibility of getting concorde flying again, the consensus (by BA/AF concorde engineers) was that it was doable but not on any BA fleet remnants without a major financial input to the point of rebuilding the aircraft. Spares etc are a problem now. But (a big but) the business case is very weak and inevitably corners would be cut. I would point you at the accident report for the Thunder City EE Lightning which crashed in South Africa killing the pilot, the cause was maintenance not being done to a sufficent standard. No single thing but a build up of causes which by themselves didn't seem to matter, a chilling read if you have an hour to spare. http://www.caa.co.za/resource%20center/accidents%20&%20incid/reports/2009/8706.pdf An accident waiting to happen............