Hi and welcome
Here's an up to date P2 service invoice:-
viewtopic.php?f=64&t=49237
The JDM (import) has a 70 litre tank and the UK cars have 80 litre tanks I believe. Avg 25 won't be far off but obviously depends how you drive it and if you're like me (I do about 7k a year too) you won't get 25 all the time because you'll want to "drive" it each time you get in it With restraint I manage 26/27 mpg. Mind you, as already been said you won't stop smiling from the moment you own one Time for a change buddy, personally I dont think you'll regret it.