Ask for a Special VFR Clearance via Hatton Cross and M25 Junction 14
not above XXXX legal feet.
If no traffic there is no reason for NATS not to provide the clearance.
Obey the 1000ft and the 500ft rule at all times.
Do not at any stage ask for "an approach to" or "overflight of" or the use of any of the facilities owned by BAA.
It has nothing to do with BAA - they do not own the airspace - to say they can have any "ownership" of the empty airspace above their property creates a dangerous precident for NIMBYs.
Good Luck!
Regards,
DFC