24 hours since I asked a reasonable question and they haven't bothered to respond...
While I was waiting

I found
this which you may find interesting.
It details the
Public Funding that Duxford/IWM get and what they are supposed to do with it.
An interesting snippet:
2.5.1 to increase participation in culture and the development of the museum sector, the IWM will promote and deliver a wide, lively and educational programme of public activity to develop further its audience and its reputation;
Specifically the Museum will:
Deliver an exciting and diverse programme of temporary exhibitions and events, which will be inclusive of the 60 th Second World War anniversaries of D-Day and VE/VJ Day and the centenary of flight in 2003
(my bolding)
or this one
3. Levels of Public Investment for 2003-2006
3.1 The level of Government funding for the 3 years 2003-2004 to 2005-2006 includes the amount announced in the Secretary of State’s letter of (22 nd October 2002) plus any further amounts agreed prior to the signing of the agreement and will be as follows:
£ms 2003/04 2004/05 2005/06
Totals 16.541 17.491 17.811
Interesting.
Hope they reply soon - you never know what you might find on the Internet