Cheers for the replies. I checked the oil after a 35 mile ride. It was done immediately and 10 minutes after stopping. Both times the dipstick showed the same reading. I checked it by having the bike upright and the dipstick not screwed back in.

I was just a bit worried about running the bike for 600 miles with the dipstick level at empty, but as it only needed 300mls, hopefully the longevity of the engine will be unaffected.