I've had mine for a couple of months and the most i've had is 260-270, the least was about 230. Although my ave consumption is getting better as the engine gets loosened up - car had 2500 on it when i bought it, now has 4500.
Depending on the price if petrol you're looking at £55+ for a tank.
Iv got a 2006, 15k miles, duno how much I get out of a tank cos I never fill it up, (I get bored easily).
I never get more than 18 miles to the gallon tho. Possibley 19. Mines modded tho so I spose that could make a difference...?