Pulled the pots and switch out and spent a fair bit of time testing for shorts etc. Tested resistance levels on the pots without having a complete understanding of what results to expect. Measured the same short between the middle leg of the volume pot and earth a dozen times while working under the misguided assumption that this was what was expected. After finally coming to the conclusion that it was not expected, I squinted through my poor eyesight of an old man and my glasses that are obviously requiring a prescription update and managed to spot the tiniest sliver of solder that had managed to create a short. It was like a very thin spider web strand that had somehow managed to string itself in the course of my inadequate solder job. I flicked it away with my screwdriver, and voila! ... sound. Fixed up a couple of other dodgy solder joints and put it all back together and it's all working.

Got some dreadful buzzing on the fretting the first few frets and the action is already too high for my liking, so time for truss rod adjustments. I haven't even looked at leveling the frets - I didn't have to worry about that on my first kit but it may be needed here.