Fuse 3? counting from which side?
I counted from the top, same as photograph in workshop manual. Schematic has is upside-down perversely.
Unless daughter decides to come I’ll take on local VMCC run tomorrow and see how it behaves. If she comes I’ll be taking the 850GT which has a dual seat.
Yes fuse 2 on the wiring diagram = fuse 3 in reality, strange but true. I used to mess up with wires to coils, they have red to RH and green to LH, if you were a sailor you would know that is the wrong way around. Also the wiring diagram shows the LH coil on the right and the RH coil on the left. Confused, you will be 
Just to update, in case it helps someone else out. Having cleaned up the fuse box connections and all the fuses, this problem was still there. With it running on the centre stand today I waited till the fault appeared and checked a few other functions and it seemed that everything on fuses 1-3 was affected. This pointed to the key switch so I dropped it out to check the connections, and actually found the switch body falling apart. Took it apart carefully, cleaned inside and bent the little tabs back over. Seems OK now…
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Flippin’ 'eck. 
But shows how it could be something you won’t think of. Good find.
Flippin ‘eck indeed. That’s proper Sherlock Holmes deduction. I can see how a dodgy ignition switch can cause your lights to fail, but why did the ignition warning come on ? Iwould have thought hat as you had effectively switched your lights off the charging should be better not worse. Or does the charge system also run through one of those fuses ?
The charge light is “balanced” between the alternator and the ignition switch feed, so if either side disappears, the light comes on. Probably will have electrical engineers cringing but I’m a mechanical engineer and that’s how I understand it. In this case, the Fuse 3 supplies the dash warning lamps (including one side of charge light) and the headlight. But, Fuse 3 gets a common ignition feed with Fuses 1 and 2 which supply the brake lights amongst other things. It was not obvious whilst riding that I was also losing the brake light, but once I had the fault with the bike on the main stand I see it. There was never any issue with the alternator keeping the battery charged.
It’s just logical diagnosis really. After I’d initially thought that it was only the items fed from Fuse 3 and cleaned up all the connections round that without success, it’s a question of working along the circuit. As it affected everything on Fuses 1-3, which are all supplied from the same terminal on the keyswitch, it had to be somewhere along that wire. Glad it was the keyswitch and not the connector under the tank.
Of course I haven’t been out for a decent ride yet to prove I’ve fixed it. Might do that in daylight first, just in case…
My thinking is that the charging light needs a feed from the +ve circuit via the ignition switch to work, when the alternator is putting out enough current the circuit is balanced and the charge light goes out. With no feed current the light will not light up.