What about going back? Is there a procedure for getting straight from WW ATZ into the Heathrow zone, without having to float around in the swamp OCAS with all the people wanting Farnborough clearances?
There are two ways that I know with various success rates. I have only done 1).
1) When ATZ traffic is light, is after takeoff call Heathrow whilst remaining inside the Waltham LFA. If a clearance is granted then you're good to go. If ATZ traffic is heavy, you may decide it's safer to exit the zone, turn back on yourself and ask Heathrow over the radio.
2) Before startup, telephone 020 8750 2578 or 02380 401 110 and ask for a VFR clearance window for a WW departure. Someone takes your details. After departure and clear of the circuit, switch frequency and you should be good to proceed.
If we don't take part in protecting GA access to infrastructure, the smaller aerodromes will be built over, the larger aerodromes will have exorbitant handling fees and awkward procedures, and airspace will be over-classified to Class A everywhere.