The key thing is to use the Insolvency Service website (http://www.insolvency.gov.uk). The examiners at the OR offices use the guidelines contained on this website, so it is straight from the horses mouth.
Probably the best link I can give you is this one:
Peruse this website and you should make sure that your income and expenditure fits in with the guideline. If anything, these figures may be slightly out of date and we know prices only go up so things like gas and electric should use up all the allowance if not more. For example, I bet you didn't know you can put down £20 a month for haircuts?! Best wishes.