Thanks to all. I've spent the weekend doing the upgrade. I bought all the cable, relays, fuses, and connectors at an automotive electrical factors, all in at £22. I had looked at all the web links supplied before I took the plunge, so I was confident I could do it, but it was a feeling of relief when I turned the lights on and it all worked! I'm now only losing between 0.5 and 1 volts at the headlamp, so the increase in brightness is significant. That said, I still have a question. The earth/ground wire in the original set up remains in the same position. I presume it goes back to the frame somewhere, but I haven't traced it yet. I ran new 4mm cables back from each relay direct to the battery to provide the best route, but I'm now wondering if I disconnect the original black earth wire and connect it to the new earth cable, will I be causing any other issues?