For those who haven't fallen asleep with this one an UPDATE... Finally got the bike back to Norman (real privilege to meet this wonderful chap) and he tells me there's signs it has been run ethanoled fuel, must be by the previous owner as I used 102 octane ethanol free, with blisters on the fibre tank and carb needles gummed up with brown residue (that's €200 wasted on a so called 'professional' clean in Germany). So he got the bike running on the right cylinder but still problems on the left. Ignition is spot on so he is going to investigate further. More to follow...
I've put four different sets of new spark plugs in the bike without success. Think Norman believes it's a failed electronic part but will await his investigation.