I got hold of a second hand G25 wheel and hub, as I had to butcher the original to wire up the QR hub. As well as allowing me to put the whole lot back to standard, this gave a couple of spare wheel buttons which I mounted to the brown wheel at the top of this thread and wired it up to work with the QR hub the same as my black wheel.
Also my brass encoder wheel arrived this morning. The original appeared to have no cracks but it was loose. It was not quite falling of, but was turning on the shaft and pulled of with virtually no resistance. The new brass version was tight (very) and took some care to fit, but this isn't going anywhere. So the wheel should last a few more years and remain accurate.
While I had the top off I used a circuit tester to find where the break was, and it was in the wires between the wheel and PCB. I found a piece of wire to bypass the broken wire, but decided to remove the PCB to give me more access, I pulled the wire out of the hub ready to bypass and noticed a cut in the sheathing where it went through the leaf spring for the paddle shifters. I peeled the covering back and was presented with this. All I needed to do in the end was put in a short piece wire to bridge the gap. Put some extra protection over the wires and this time all should be good to go with 2 functioning buttons on each wheel.
I'll be putting all this back together tomorrow, so all should be up and running for my next race. All this has given me something to do while I am stuck at home shielding and has saved me a few hundred squid for a new wheel. Plus I get to keep using my full size wheels.