well according to the specs the tank holds 3.4 US gallons and is supposed to get 46Mpg stock. I would pull over grab a drink, have a smoke and fill her up about every 100 miles, but thats what I do with my Interstate with a 4.4 gallon tank and the same engine. I hate seeing the yellow low fuel light and only have once.
I think I'm getting around 40 mpg, but I have the cobra pipes, air intake and I2000R installed.
I think the low fuel light comes on when you have .9 gallons left in your tank. So you should have roughly 40 miles left before you go dry.
There haven't been any Fury posters on these forums yet besides you, that I know of Ghost. Sure wish we would pick some more up.
My fuel light usually comes on right around the 120 mile mark on the trip odometer. I've owned my bike since May 2009. I have Cobra swept pipes, an S&S intake, and a Power Commander V fuel injection controller and average about 42 mpg. I run 87 octane gas and always add stabilizer to avoid problems with the 10% ethanol that is added in the U.S. That's probably not a problem for you in the U.K., Ghost.