i am trying to sort out a settlement now, not easy, but so far this is the advice i can give-
1- do you have a clause like mine that states you can not offer a settlement till after 24 months, if this is the case your ip will have to have a creditos meeting to have this overturned and with good reason- mine is just going through that stage.
2- you have the equity clause which i dont cause i rent, but creditors can not rely on this, whos to say poperty prices will go up in 4 years, they could have we have seen go down as well, just like Andy dave said to me they can not count on payrises.
3- you have to prove you have the funds to pay for the early settlement which i have done and explian were it comes from, as my ip states it costs money to hold the creditors meeting.
4 - i worked out my settlement figure, very much the same as you i times the amount by the months remaining and for each complete year left took £1000 a year of as this would have gone to your IP.
Hope this helps, i am going to keep posting on here as mine hopefully progress