Stands are an issue,SOU needs 737/320 size stands X 5 at least,back tracking and holding for 20 requires time,delaying outbound at least,read :
AirportWatch | To conceal the real number of aircraft noise complaints, Gatwick now just records one per person per day
New airlines will simply not come without enhanced airside and promoted routes,vueling,volotea for example.
Expect little progress until there is radical change!