Welcome to the Forum Brokenreason,
As you stated HSBC are a prodominant creditor, they hold 72% of your overall debt. HSBC are different from other creditors they ask (where they are prodominant) for a minimum dividend of 40p/£.
In your case you will need a disposable income to be c£335-350. You mentioned your income but does your wife bring home any income (inc Child Benefit & Tax Credits etc)?
When you are calculating disposable income be sure
not to include any monthly minimum payments that you are making, it should only be monthly income minus living expenses (food/bills etc).
Your mother being your employer should not be a problem, can you provide payslips? or a letter of employment?
Best Regards,
IVA Experts
http://www.iva-experts.co.uk/