I'd say that two major home platforms were Spectrum (rather, its many clones like the Pentagon) and BK series (BK-0010, BK-0011) -- market was flooded with former and the latter was mass-produced and could be actually bought in a shop. There's demoscene for both of these, see f.e. https://www.youtube.com/watch?v=BLCjzHAy9Ec (Insult gigademo for the BK) and https://www.youtube.com/watch?v=oUipQfxURwk (showcase of several Spectrum demos from Assembly'2011).
The UKNC (on the screenshot) was an educational machine and I'm not sure how many were sold to general public; the DVK series (screenshots earlier in this thread) was a professional machine and generally wasn't available to the public at all. Of course, either could be 'obtained' if you really wanted it...
