A new arms length-state owned company (London Airport Limited) would buy Heathrow, Stansted, Gatwick, City, Southend, Luton, Southend, Manson, Biggin Hill, Ashford and Cambridge Airports (and nearby hotels, offices and other airport related facilities)
First up, welcome to pprune! Secondly, interesting username choice, might not be the best choice (!) Maybe selecting something less contentious, to make it clear you are not speaking on behalf of the company?
As to the point, each of these private companies has a market value that would need to me matched should a purchase be necessary. The government has no business hoovering up private business in a free market, and even if they did, we sure as He(ck) don't have the money to do that!