I had a look and there is another page for C5's with a slightly different wiring setup. It all became clear then.
Glad to say the indicators are now fully operational!
The more I get involved in this machine the more I appreciate how misrepresented and how well engineered they are. I originally bought it as a bit of a joke, but now I see it as an important bit of motoring history much like the Citroen DS, Mini or Jaguar E-Type. The very good Classic & Sportscar article sets the record straight now. Okay the motor is a bit weedy, but a stronger motor would have probably raised more legal obsticals.
I must admit I didn't realise the indicators were so rare and pricey now - I think they are probably worth more than my C5 itself
Not surprised that some members have retrofitted adapted car ones!
Now for the horn fitting....