I would first of all contact your Supervisor and ask that an Income & Expenditure review be carried out following a change in your circumstances.
Is the job in the same area as your current employer? Are there no additional travel / fuel expenses likely to be incurred in taking the new job?
I would also check the terms of the proposal ... specifically
What does it say about repayment to your creditors. I assume currently it will say XXp in the £ after five years. Are there any terms in there regarding the maximum return to your creditors? More often than not it is 100p in the £, but there may be instances were the proposal or modifications word it that the maximum you would repay to creditors is 100p in the £ plus Statutory Interest, which I believe currently runs at 8% per annum. There should be some clarity in the proposal on the extent you are to repay creditors
Check what it says there.
It may well be that by increasing the level of your contributions you are able to conclude your arrangement sooner, depending on the maximium amount you are required to repay.
When you say you would be better off going back to the old way as you were able to meet repayments - does that mean you were meeting just the minimum repayments or were you paying the full amount off each month? If you were paying the minimum amount off each month, was the amount you actually owe going down or was interest accruing at a higher rate than minimum payments? If it was decreasing the amount you owe, then you're never going to be better off unless you can make a substantial dent in the liabilities, but I don't know how you would do that save snowballing the debt.
At the moment you have the comfort of knowing that interest and charges are no longer accruing on your liabilities. If you exit the IVA by way of default, you will lose that comfort as the interest and charges would start to accrue again and they would be back dated to the date on which they were frozen. Admittedly in your case it is only one or two months ago, but you will notice because of the penal rates of interest applied.
If you were to go bankrupt, you may still have to make income payments to a Trustee in bankruptcy. These will probably, but by no means guaranteed, be lower than the payments currently being paid in to the IVA. Your 6 year credit blip on your record will also start over on ther making of a bankruptcy order.
Bankruptcy may affect your employment if employed in certain sectors and certainly if in the financial services industry.
There are many things to consider and I am sure that someone will probably add to the list I have given.
Tell it like it is.