I don't think that's entirely true. There is a difference between using 'branded' names when using radio transmissions, etc as opposed to 'proper' names which has the potential to cause confusion to those not familiar with the name change. That should in no way affect the commercial aspects of rebranding an airport to raise its profile to the travelling public.
The CAA have said that for airports such as Liverpool John Lennon, they will be referred to in all official CAA correspondence by its official title, not its branded title.