Got a replacement speedo cable with the right connection - here it is next to the one that came off. I think it's clear it's much longer! This makes alot of sense as to why the original stopped working etc - it was going through too tight a bends etc to stretch to fit.
Replacing it with the new one was straightforward enough but I could do with the correct grommet - I will "make up" a gap around the grommet and the cable with some "dum dum" paste but the correct one would be a much snugger fit.
Anyway, with it all fitted I now have a speedo that works again so that should be enough on this car as I want to turn attention to BRP which should be the main priority apart from ----
There is still a judder through the steering wheel, sometimes on braking, sometimes not - hmmm.
Also, I am aiming to do a 12 car rally which will be at night so I am thinking about wiring in relays to the headlights which would need to be done next week as its only 2 weeks from now!
I might take the fan off as well to help the car warm up and release a little power - there's not much chance of a heatwave anytime soon!