Cobham and Serco are two powerhouses as big if not bigger than Peel, if Peel did try to close the airport, they along with the other above mentioned companies, would soon stop them.
SERCO may have Peel in a fight, but Cobham would get a kicking.
Also, does it matter to SERCO if MME is an active airfield? Either way, I'm sure Peel could find a way of getting what they wanted.
TNT are the only other residents of any substance, and they don't need MME to be an active airfield - the rest are lightweights.