Ehegarty: as you clearly live near FH station then all I can do is sympathise. There has been an increasing problem of parking in the streets around Honor Oak Park station since the Overground service started.
Apart from putting up signs like "24 hour access required" you could try one of these, which may make your driveway-obstructers go elsewhere.
BREAKDOWN TRUCK PARKING ONLY
DANGER! FORK LIFT TRUCK IN USE!
TRAFFIC WARDENS REFRESHMENT POINT
CAR BREAKERS YARD ENTRANCE