Rule 5 (3)
(c) Special VFR clearance and notified routes
(i) Any aircraft shall be exempt from the 1000 feet rule when flying in a control zone under a special VFR clearance issued by the appropriate air traffic service unit, or when operating in accordance with the procedures notified for the route being flown.
(ii) When flying in accordance with this exemption landings may not be made at other than a licensed or Government aerodrome, unless the permission of the CAA has been obtained.
And some of Blackheath is in R160,