Hello Ruffles,
Its a timescale thing. The original move from Lippitts Hill to North Weald was precipitated by NPAS and may arguably be placed at the feet of the COO. That was the several years ago DH mentioned.
The Lippitts Site was relatively expensive [rental/lease] but what is being suggested is that the prime mover was breaking the bond between the Met and the NPAS unit - force jealousy.
Lippitts has been in use as a Met helicopter base full time for over forty years [53 on and off if you include the army trials] and remains firmly Met Territory even though a border move actually placed it in Essex Police area since 2000.
You are correct that the Met have/will/might [it has not happened yet] precipitate the return to Lippitts Hill and the site has been maintained ready to accept them on that basis. Whether the immediate neighbours will scupper that - they have had many noise free months - and whether the recently reported move of the Exeter EC145 to North Weald is a bargaining chip only time will tell.
The only problem with being a 'fly on the wall' in this situation is that you probably also need to be on many walls at the same time in this zoom age!