Ended up buying a twin (H1) HID Xenon setup (Extreme HID 6000K on the box) from
www.visionbulbs.com, links into the existing H1 bulb sockets. The ballasts should fit neatly on the mini shelf under the headlamps with a slight mod of the supplied mounting plates - I hope. What's in the box? A pair of Xenon bulbs, pair of ballasts with mounting plates, relay and harness. My only concern is whether the lights-always-on GSA I have will blip the Xenons when I start the bike. Appear to be a bargain at £127 (includes 10% discount with "VBVIPDSCT" discount code). ps Note they did take 10 days to be delivered.