Ozflight. Not too sure what you mean by "fixed landing gear". The last one I flew the gear came up just fine.
At 41,000 feet, approx 55 tons at M.78 the 700 burns around 1900 kg/hr, give or take a couple.
At 41,000 feet, approx 60 tons at M.78 the 800 burns around 2200 kg/hr, ditto.
Some of the Virgin 800's have 26K engines and some of the 700's have 22K engines. The extra 2 K gives around an extra 5 tons of take off weight when needed (short rwy and hot etc).