You cannot compare UK companies with classic US companies like Origin, early EA, Infocom, Sierra, Sir-Tech, Mindscape, Broderbund, Synapse, Microprose, Omnitrend, Activision (in their prime before Activision set up a UK software house and went downhill), Datasoft, Lucasfilm, Sirius Software...etc. Those companies produced high quality 8-bit software by very talented programmers...Joe Vierra, Bill Hogue, Sid Meier, Richard Garriot, Doug Smith, Anne Westfall, Dan(ny) Bunton, Stephen Landrum, Bill Heineman, Edward Hobbs...etc..... their games sold wordwide, softs by Ultimate PtG on the other hand, did not.
Some of those companies actually had softs out on Spectrum, eg Activision, Microprose, well, they tried, what can one say....Codemasters on Spectrum, that'll work, Sir-Tech, obviously, that would never work.