I would recommend talking to the free debt charities like Citizens Advice Bureau, National Debtline and CCCS (and payplan) before using a company that charges for it's services. They will be able to offer you independent advice which will not have anything in their interest (they won't be charging your 15% on top of your debt).
I would recommend the original poster (cookie) gets a copy of their Credit record (for £2) to see what information it holds.
As veloxuk has said it is likely to affect your ability to get any further credit especially in the current climate where an 'excellent' credit score isn't a guarantee of getting credit. Lenders are far more careful about the risk now. (words stable door, horse and bolted come to mind).
The information will typically last 6 years, but you have spent the last 2/3 building up your credit rating again, and I would continue doing so.
HTH
Sparky.