Finally my ignition unit arrived, actually after I physically collected it, so I had to make a mounting for it. I made a cardboard template to house the Interspan unit and transferred the sizes onto 2mm plate, trimming and folding it (harder with steel). Painted it with etch and then 2k black so I'm about done now. The bikes now running and this is leading up to that clip.
Anyway, it's a total loss 20 volt type system, that will run the bike for 8 hours continual use, so is more than adequate for what I will ever demand from the bike. I doubt I'd want to ride this for more than 2 hours, so being practical it's a good solution.