Repaying Overpayment of Student Grant

I posted on here a while back as I was being harassed by debt collectors regarding an overpayment of my student grant. To cut a long story short, in my final year of Uni I became means tested as the recession hit and my parents couldn't help me out financially any more. I was awarded a grant based on my parents' disposable income, but Student Loans are now insisting I was never entitled to the grant and they want it back (£2500).

After many phone calls and investigations I managed to get my claim re-assessed. The original grant was paid to me as my father is self employed and predicted he'd only have 15 hours work a week, which was only just enough to pay bills, mortgage etc when combined with my mother's income. Therefore the grant was awarded to me based on their combined disposable income. In the reassessment, they said I had to pay the grant back based on their gross income - so they've based it on a completely different criteria! Also my Dad actually had no work, not the 15 hours he predicted.

Anyone had any similar experiences or any advice in how to proceed? I'm considering financial ombudsman?

George