Yup, I'll get a couple of bottles of the stuff.The oil quantity in the gearbox is 0.9 litres, the final drive 0.18 litres, so if your going to fill to spec you need just over 1 litre.
Over here the cost of the oil is approx £14 per litre, so no harm having some left over for next year.
http://www.opieoils.co.uk/search/go?w=S ... &view=grid
Just noticed that the same company, Opie Oils, sells it cheaper on Ebay (cost + P&P):
http://www.ebay.co.uk/itm/Castrol-Syntr ... xyBotTbNYa
Wonder if I can use the same oil on my R1100S?
Looking on the newfangled interweb it recommends a "Hypoid Gear Oil, SAE 90, API class GL 5" for gearbox & final drive.......