"To change the use of the land they'd need to get planning permission from ???"
Well, yes, from the local planning authority (council), except that:
1/ a housing development would offer substantial council tax income, as would industrial when the new business rate regs come into force.
2/ there would have to be very good valid planning reasons to refuse permission, or risk the expense of a planning appeal, which would certainly be lost if there weren't good planning reasons for refusal.
3/ as a nominally regional facility, any application might be "called-in" by the Sec of State (currently Mr Pickles) for determination by him rather than the councils.