Honestly, if you are managing each month then i wouldn't change what you are doing because you sound like you are making progress into clearing your debts. I take it you are not incurring any more?
The thing with a debt management plan is that it will fuck up your credit score, which if you are paying everything off on time will be ok at the moment, ours was fucked and we were on the verge of losing the house anyway so we had no chioce.
Also, you need to consider what you would do if you up your mortgage and there is a hike in interest rates, this is what i dread, will be screwed if this happens.
If i were you, i would
If you can afford to, and i mean really afford it, you can't live on bread and water! Carry on as you are, if you are making inroads and not paying any interest. Obviously cut the cards up! If you are struggling, consider a debt management plan - or at least contact one of the non profit making companies: National Debt line, CCCS, Payplan (we are with payplan, they are "ok" they do try and push other products like cheap loands, err, no ta!!, but they dont charge for the services). Where a debt management plan is useful is if you have multiple creditors like we did. So if we had a duff month (my DP is self empoyed, it happens) we were incurring loads of extra charges, if you only have one card it might be better to stay as you are, because i thnk you do "default" once you go into a DMP, im not sure on that though, you might want to check.
Please feel free to PM me if you want any more help, i think ive been through it all :( But as a result, i know my rights.