The transplant was a success! I now have a full volt higher across teh rev range, a healthy 13v at 1000 rpm and just on 15v at 4000, where it tops out. With the headlights on, take off a half volt or so. The voltage is also a bit more stable too.
I took the opportunity to clean up all the wiring around the battery area, someone a long time ago, who knew very little about electricity, had made a huge birds nest in there! Now it's all neat, and I have 5 fuses I can actually find and reach! I also found an earth wire that wasn't connected to anything, could explain the couple of times I've had smoke issues and partly melted ground wires here and there!
Is there any reason I shouldn't leave the fuses in the reg/rectifier curcuits?
Regards, Andrew.