I know people always recommend doing a forward-looking budget, but in my experience (as a business accountant), you need the data of the past first. Not for finger-pointing, but for some proper information as to what you "normally" spend. Knowledge is power!
I usually recommend people go back 3 months, get full downloads of their transactions from online banking, and analyse ALL the in's and out's for the 3 month period. That will immediately highlight how much you're spending on the different utilities, phone contracts, monthly subscriptions, supermarket shopping, cloth shopping, car costs, TV/Sky/Broadband, coffees/cakes, work lunches, takeaways, personal grooming, gym, loans, interest, etc etc. You can then make an "informed" choice as to whether each category was actually "worth it" to you. You can then make some very simple savings by cutting out the worthless crap.
You can use that data/knowledge to make your forward forecasts as to what a more realistic level of spending would look like, initially based on just cutting our the crap, but then you can refine it more by making harder changes, i.e. getting cheaper car insurance, cheaper utilities, cheaper car lease, cheaper broadband/sky/tv, cheaper phone contract/sim, etc etc.
Then you can start to see what surplus you may have, and plan how you use that surplus to best advantage, i.e. paying off the most expensive (interest) credit/loans/HP first, etc.
It all starts with the data as to where you are NOW and what's been happening for the past few months. Pointless going back further, as it's just raking over the past mistakes. It's all about changing future behaviour, understanding your finances and where the money is going, understanding how the debt is building up via high interest and charges, etc., Knowledge is power, so you need a really good handle on where you are, and then you can move forward in the right direction.