It would be good to fully understand how the UK framebuilders each became first aware and then went on to build that first bike suitable in their thoughts for 'offroad'. Was it perhaps well travelled customers bringing in photos or descriptions of early American bikes or some other unique demand? Framebuilders weren't classified as frame designers back then where they? Whatever, most of the early bikes that have come through here circa 1983/4 vintage look fairly similar in their thinking, much along the Ritchey/Specialized template - was that basic road bike design what made mountain biking really take off? Surely more of a holding station until designers (creativity + engineering) rather than framebuilders came to the fore and a more fertile and liberal approach was funded by the plethora of entrepeneurial endeavours that became attracted to the opportunity.
In this regard, the UK has little originality to show for itself over the early period of ATB to MTB history except for Apps' lone furrow. Genuine artists and creatives, neither here or in the US, are guided or influenced by what we supposedly normal folk would call 'success' - they are challenged by our conventions and rigid thinking and are unlikely to conform in any or all aspects of life. Vive la difference - without difference we have nothing.