Complex sentence: Until the end of the Cold War many of the sites were retained by the government but now have been sold off to private buyers or converted into museums (for example'RAF Hack Green') and some transferred to the National Air Traffic Control Centre.
Split into simpler sentences: Until the end of the Cold War, many of the sites were retained by the government. They were later sold to private buyers, converted into museums (for example Hack Green) or transferred to the National Air Traffic Control Centre.