First off, i'm assuming its not zoned but can be considered "rural":
Not so sure about getting an outline PP. The planners will more than likely put an occupancy clause in the conditions. These clauses are no longer being ignored by purchasers solicitors, particularly when a mortgage is involved.
You might do best by selling it privately, subject to planning or, instead of doing it subject to planning, sell it with a six month closing date. If you do sell subejct to planning, put in a wording to ensure the buyer actually has to apply for the PP within a reasonable amount of time, say 6-8 weeks.