Any company that freezes or reduces interest will usually put you onto an arrangement to pay and default your account which is what would happen on a debt management plan anyway. I’m not aware of any alternatives

happy to be corrected if anyone has any personal experience?
OP- if you think you can pay off your remaining credit within the interest free period, plus keep some spare for cost of living increases- and you really need to overestimate this rather than underestimate- then go for it, but worth bearing in mind if you find out in a year you are unable to keep it up and end up going into a DMP anyway then you’ve lost valuable time. I am in a DMP through step change and currently in the process of buying a house, our mortgage with a specialist lender is about £250 a month more than if we were with a high street lender but we have only been in the DMP since summer 2019 and have just hit the time period to qualify for a mortgage (there aren’t any lenders that will currently lend to anyone with defaults less than 2 years old unless they are very small). I am glad we did it because for the last 2.5 years we have not worried about money at all because we have had someone help us with a comfortable budget. We get to redo the budget as much as we need to if anything changes, our credit is only getting better not worse and in a few years we will have paid off £65k of debt (!!) and our attitude towards credit has completely changed and honestly that is the best gift of all.