Well, I did suss out what was wrong and it's quite alarming....but not in an expensive way.
Since it's been laid up for winter, I've been turning it over every couple of weeks to make sure the belts don't get set in one position. Since the fairings are off and in bubble wrap up my loft it's been easy to use Nelly's trick of disconnecting the crank sensor and turning it over until the oil light goes out.
One day, the lure of hearing it start got too much, so I plugged the sensor in again and tried firing it up....turned over a bit sluggish, but....nothing. Gave the battery another charge and it turned over faster but...nothing.
OK, try the age old checks for fuel, sparks etc...but I didn't need to look far, I popped the fuel cap and found the tank was bone dry. I had put it to bed with about a litre in the tank so I was suprised to find it had all gone in a month or so. Evaporation? wouldn't think so....
Anyhow, I sploshed a little fuel in, the pump primed and the old girl started at the first prod of the starter. I warmed it up...no smoke...no drama...nothing. Kept it running until it was good and warm and the fan cut in. No problems at all. Then I got to wondering why the fuel had run dry and started checking for leaks. Sure enough, one of the hoses is weeping....ever so slowly (even with the pump going it's about one drip every 10 minutes). That would explain why the bike always smells as if it's just come back from a run...funnily enough it's not a raw petrol smell but more like the mix of hot oil and hot brakes. Anyway, I reckon what was happening was that there was a very slow drip of petrol when the bike was standing that splashed off the rear of the crankcase onto the surrounding bits, a real slow seep so that there really wasn't any petrol pouring out and not so much as to soak the area or make it wet...just enough so that all the volatile stuff evaporated leaving a bit of residue to burn off.