I am surprised a DMP was chosen in the first place --- if all creditors continue and all freeze interest you are looking at 23 years until you finish ! I suspect that StepChange would shortly be suggesting an IVA anyway.
On the few facts you have presented an IVA would be a better solution (but, of course, we are not privvy to the full picture). You might have a creditor that, at the time, Stepchange knew would be resistant to an IVA. Either a standard 5 year agreement, or, as you suggest, a F&F IVA ---which, in a nutshell is an IVA consisting of one lump sum payment giving the usual protections.
As to amounts required, that, I am afraid, is a guessing game. If you were to enter into a standard IVA with the same payment the creditors would be getting around £11,400 plus another £2280 in lieu of the equity (assuming you get the extension to term rather than being able to release equity). So in the region of £13.5k. Of course, they might not agree to the arrangement, or you might be able to release equity, so they get a little more. Out of that figure will come around £2.5k in fees. They will also be spending the next 5 years collecting small dividends and spending time and money doing so. So they would see about £11k.
Say you offered £20,000 in a lump sum: They would see around £15k of that but in a lump with much less faffing around. So, on the face of it , a better proposition.
Of course you need to be able to go in with a strong offer. I would suggest a chat with Ryan and / or Shaun, who are whole of market brokers with experience of dealing with adverse credit, and who might have access to products to assistm in such situations. They can be contacted through the info on their profiles here:
Ryan:
memberlist.php?mode=viewprofile&u=18488
Shaun:
memberlist.php?mode=viewprofile&u=22837
If you
sell the property the creditors would expect the lion's share of the proceeds.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014