Daz,
Knowledge is power. The first building block you need is to understand fully the "bad credit" you mentioned. What you din't want is to find a deal then have it fall apart because of credit history.
So, if you haven't done it yet register with Experian and Equifax. They both have websites with .co.uk at the end. You can get your statutory report for £2, or a more user friendly version for (I think) about £8. Alternatively, one of them has a subscription at £40 a year and you get e-mail alerts and text messages on anything significant that happens with your credit record (surprising how many companies and organisations check up on you).
If you have a CCJ, this is the most problematical. With this the best you can do is to pay it off asap get it marked as satisfied then add a personal statement as to why this occured.
The most important thing is to start showing responsible handling of credit now. To do this you need a credit card. Depending on the level of "bad credit" you mentioned, your strategy will have to be adjusted. Ideally what you want is a credit card that you use, and alternate between paying the full amount then every few months to not paying off some then the full amount the following month always making sure you pay on time. This will give you a string of "000000" on your credit record which other lenders will see and higher your score as a result.
Second and more easy is to open a bank account with particular institutions. My main personal bank is HSBC - they do squaddly ditt for my credit record. I have others, one of which is with Alliance and Leicester (horrible bank though). They are vey good for your credit file as every month if you have not done an "unauthorised overdraft" you again get a "0" on your credit file. There must be others that do this as well.
On your credit file, the more recent stuff carries more weight so the recent "0"'s are important.
Once you have established a responsible credit record, NMD deals will be easier to find. However, unlike the USA, True NMD deals are difficult to find. In this country many people that talk of NMD deals mean that you have to have money to do the deal, but once done you can finance or re-finance to get all your money out. So in effect it is NMD after the deal.
Click on the link to look at the blog of a
maverick