Dennis, would that be Peter Michael who - so Wikipedia tells me - founded both Micro Consultants and Quantel - never knew what they did till I read the article on Wiki!
Sav, a mere tickle compared with your heard work!
Yes I can only remember those two as regular helicopters at Biggin, and rather more when the British Grand Prix was at Brands Hatch.
The two blister hangars beyond Express contained some interesting airframes. the far one as you say had the Air & Space 18A plus a dilapidated Commander 500 both owned by Interflight - Chris de Vere was certainly associated with Biggin Hill.
The other blister hangar next to Express contained an American Lear 25 for a bit. Both blisters collapsed under the weight of snow on separate occasions in the 1980s/1990s.