Savoia and bastOn,
A short input from a long-retired Crab, who just might be acceptable to bastOn since I was on 705 for 3 yrs '63 to '66, remembering many happy Sundays out on (in?) Seahawk's whaler from Falmouth to many different pubs up many local creeks, skippered by the bearded Dave T - who IIRC hung on too long to the skids of a Hiller when the little old lady took off on one Air Day and was well bruised.
Anyway, to the point - yes that HCC8 was indeed the RAF's VVIP version of the RN Mk7. There were just the 2 on The Queen's Flight.
All RAF Whirlwinds, and Wessex, always had an even Mark number - RN always odd numbered. Our Whirlwind Mk4, which I was lucky enough to operate in Malaya (before your Borneo days bastOn) was same airframe as the RN Mk3, but we had a smooth 9-cyl P & W Wasp instead of that thumping 7-cyl Wright Cyclone. There were also 2 HCC12s (VVIP version of the Gnome turbine-engined Mk10) which replaced the 8s on TQF, until one crashed after main shaft failure in Dec '67. They in turn were replaced by 2 Wessex HCC4s (ok you're way ahead of me now, they were the VVIP version of the RAF Wessex 2s), and these did sterling and very safe service for nearly 20 years.
Enough.