Thanks guys. I thought this thread would instantly descend into a massive piss-take but so far so good!
I'm pretty sure the ground is level, and that I'm not pushing or pulling the bike. I put my XT660R on the stand all the time and that doesn't have the same wobble.
I'll look into it a bit more this weekend. I'll find a dead flat bit of ground or maybe head to my dealer for a bacon roll and to try to get a discount off some auxiliary lights and check out their demo bikes.
Engineer is right that as a tight-wad non-subscriber I guess I can't PM people to take up their offers of a comparison. I will therefore have a rummage down the back of the sofa and see if I can scrape together a few quid. If not, is it possible to subscribe for the 3p per day that the site advertises?