Great minds...
... let other people do the thinking.
Pots should be arriving in the next day or so, then we'll see how well they fit my homemade knobs. I was just going to get a wiring diagram off the web, there do seem to be plenty kicking around for a single p90 and two pots. Going to be fun installing everything though, only read about the ground wire through the end block a couple of days ago...