Promise kept.... It was easy peasy lemon squeezy!
1) Changed the battery terminals around (remarked them + and - accordingly.) 2) Then disconnected the 'F' and 'D' leads on the regulator. Flashed the F lead across the main battery feed 'B' 6 times to reverse the dynamo polarity. 3) swapped the wires going to the ammeter. 4) started the beast - everything worked as normal - heater / wipers etc all ran the right way. The only thing that didn't was a small (modern) pump motor on the washer. Swapped the 2 wires and it worked perfectly.Even the horn didn't go "PEEB" as expected.
Oh I forgot - as it's a carawagon there were two fluorescent strip lights in the back: they needed the 2 wires swapping as well.
Great stuff - it took less than 20 minutes :-)
Chris floaty thing