Well I took the left side cover off to have a look see at the starter's connections and the neutral switch. Never any problems there, it would always go on reliably when in neutral. But it looked a little cruddy so I undid the male lead that goes in the ground clip, looked very good. So I stuck it back in and no neutral light, but it would ground okay to the engine case, hmmm. I undid the phillips screw holding behind the rubber cam and inspected the two posts the little band presses down to. Is this supposed to actually touch these two posts? Mine doesn't appear to be, and was 1 or 2 mm misaligned, only catching the head of one of them. The one that wasn't touching was covered in crud, the other shiny. They both look a bit worn down. I bent it slightly to realign it, cleaned the one dirty post, and reinstalled. Lo and behold my starter turns, although I still get a click on every third thumb of the starter now. I think a new switch is in order.