Hi Doug and welcome to the forum
When you consult an insolvency practitioner they will go through your income and expenditure with you to see how much you can afford to offer to your creditors. It is usual to need to offer at least 25p in the £ as a minimum dividend, so on the level of debts you are carrying you would need to pay at least £360 per month to also take account of IP fees - but obviously you would have to pay more if you could afford it. if the IVA is accpeted, the will write off all the remaining debt at the time you make the final payment usually in five years time.
If you are living at home with your parents, and have no assets, have you also considered bankruptcy proceedings? An IVA ought to take no more than 6 weeks to set up for you, and possibly less in your case which seems relatively simple.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk