Thanks Nealh, I am definitely getting old enough to be a leg end!
josh42ad, we did not take any pictures when we opened up the battery.
A fellow American posted on my Yamaha Battery/Charger Problem thread, spiwrx, who made a neater repair than my friend and I, and also took some pictures, and noted;
"In case its helpful my (US) charger wire color codes / pinout:
Charger | Battery
Yellow | Blue
Black | Black
Red | Red
Blue | White"
https://www.pedelecs.co.uk/forum/threads/yamaha-battery-charger-problem.31092/page-4
Nealh is a far more technically able repairer than me, I am more a bodge it man, and too tight not to have a go at repairing my battery/charger connectors rather than lay down £800 to buy new ones.
My battery and charger have now powered my bike and I for over 7,500 miles since the repair!
If I manage to ride the bike another 1,500 miles it will have done as many miles after the repair as before!