I met John Whiscombe at an early FT shoot I organised in the early 1980s, when he had just his prototype which comprised two BSA Mercury cylinders welded end on end; a very approachable chap. Later, a close friend (the late Emeritus Professor Mike Wright) became close friends with John and in fact guided him through the complex maths needed to determine the mass needed for John's 'HOTS' (muzzle vibration damping/timing) system.
Mike brought a couple of John's rifles to my home range. They were extremely heavy, hard work to cock, but utterly motionless during the shot cycle - not a rifle to carry around a shoot, but a superb target rifle.
From conversations with Mike I believe one UK manufacturer did explore the possibility of producing the rifle, but that fell through, and I think that may have been due to the precision on their CNC machinery not being up to the mark, and the requirement for hand finishing making the rifle uneconomic to built, especially as it offered no tangible advantage over their then PCP range.
A Whiscombe is a work of art, an example of craftsmanship at its very best, but a bit impractical for many with its mass and cocking effort.