Before you decide on either a Debt Management Plan or an IVA / Individual Voluntary Arrangement, make sure you have checked your current credit status!
This is important as it will show you what is on record about your financial history. You do not want to carry on as though this information does not exist and once you read it, things on the report seem less frightening than you thought. If anything, it is a good starting point for any debt advisor to help you from, as it is easily read by people who are reading them daily.
You can get a free credit report online from Experian in the UK.