This! Who cares how much it is, if you're worried about fuel consumption with a drunk RB for daily duties, you really need to think about it and look at buying a small daily.
United might be taking the piss a bit with their 107 "race blend"... Meh.
Put an ethanol sensor and a half decent ecu in the car. Run the car on 98 and when you want to be a clown/trackday fill it up with ethanol. It really isn't that hard.