From the link in this thread
(http://www.pprune.org/forums/showthread.php?t=258470) it is now clear that the rejection is pricipally due the fact that no clear justification for the use of hangers 5-8 was made (three potential uses were suggested).
The Planning Officer notes that "the applicant gives three possible end uses for these Hangars:
. covering parking for those aircraft that would formerly have been accommodated in the polytunnels now deleted from the application
. additional space for mechanical and engineering operations
. other industries using the hangar space with up to 5-10 further people being employed"
By specifying three potential uses, the Duchy appear to have conceeded that there is no clear justification for these hangers - if there was, they would have specificed this one particular end use and not mentioned the other two.
Having deleted the Polytunnels proposed for Aircraft storage, the first of these options appears the 'correct' end use that should be sought for hangers 5-8.
A business case can be made for hangers rather than poly tunnels on the basis of the lifespan of the 'building' and the premium that aircraft owners might be prepared to pay to have a more secure form of storage for their aircraft.