Remember that the JDM tank is smaller than the UK one......
I agree with Sarnie though, I fill up at about a quarter and it varies a lot with the type of driving I do. If you do a 50 mile motorway commute at a steady speed and then fill up with dte 20 then of course you'll get more to a 'tank' than someone who hoons accross the countryside at every oporyunity and then fills up at a quarter.