I agree that an IVA was OTT for such a debt, but there might have been reasons to which we are not privvy. However, if you allow the IVA to fail now you will kiss goodbye to the payments you have thus far made, a great chunk of which will have been swallowed in fees. The creditors will then add back on the lost few years interest and possible charges, which will increase the debt level substantially.
If and when you hit 100% of the original debt, plus fees and possible statutory interest the IVA will stop at that point.
Added to this, your creditors will be very wary of dealing with you in a debt management plan, as you have already failed to meet your current obligations by not paying over the agreed extra payments.
As things stand, providing you make up the arrears, you will be out of the IVA and debt free within about 2 and a half years. In a DMP it will be anyone's guess.
Finally, regarding the fees question: If you are with an independent company they will get fees out of both an IVA or a DMP (possibly more from the DMP as these can be protracted and are not heavily regulated). If you are with one of the so-called charity firms, they do not take fees from your DMP payments, but get subsidised by the banks for this service, so still get paid. And, at the end of the day the fees in an IVA are agreed by the creditors, indeed, these days they are often SET by the creditors.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014