This should make interesting reading.
ASIDELINES: Plans for private airstrip taking off - The Star
As far as I know, as long as you're not planning to disturb a site of special scientific interest or similar, there shouldn't be a problem and you shouldn't need planning permission, although it might be prudent to have a word with the local planning office - they're going to find out about it one way or the other.
A couple of friends got around the "hanger" problem, by errecting a "barn", which, at the time didn't need planning permission providing some agricultural equipment was actually kept in it.
Quite an expensive option these days, but it depends how long you intend to operate from your strip and whether you can persuade the landowner to meet you halfway perhaps.