For some people, however much they budget, the change in their circumstances is so great that they can't carry on paying for rent, mortgage, utility bills and so on.
If you're in serious debt, it's essential to get advice. If you live in England and Wales, GOV.UK's debt pages are very useful, including advice on what debts must be prioritised. If you live in Scotland visit Mygov.scot for information and advice.
The National Debtline provides advice for those in debt.
Independent financial advice
For further professional advice, you can look for an Independent Financial Adviser (IFA). Their services are often free, or they take a percentage of payment from a product provider (such as a building society which sells you a mortgage).
Your bank or building society may have a financial adviser attached to it, though they may be committed to selling you a product from their own range.