SVFR has always been at ATC discretion.
The flights are not Cat Z, they are normal flights i.e. filed a plan and operating in the normal way (for heli's inbound to say Battersea).
Would you prefer flights such as these to request IFR clearance into the Heathrow CTR?
I know that if my business revolved round heli flights to and from Battersea, and I have an IFR capable heli+ crew, I would file IFR via the heli lanes.
The Heathrow zone is established for the protection of aircraft arriving at and departing Heathrow airport. It is not for the purposes of excluding other flights. It does require ATC to integrate other flights especially those who have legitimate reason to require entry into the zone i.e. destination within it with those being protected.
When the Heathrow zone becomes EG-P-xxx or EG-R-xxx then flights can be excluded.
Regards,
DFC