I did do that and had a good look at it through a small X10 magnifying glass, couldn't see any obvious breaks so the wire break may be under several layers, at first I thought that there may have been a dry solder joint on the leadout wires so I tried re-soldering the joints, no luck, it's obviously suffered a break in the wire where it's not easy to get to without un-winding all the wire off the bobbin.
Looks like I'm just going to have to write-off the current set of pickups and order a set of new ones, I was going to change them out anyway for a set of ASN57's.