If you can email me at ivacustomerservices@uk.gt.com and quote "IVA Forum" in the subject line I will be happy to review your case and clarify the position for you.
As per Melanie's comments, if you can repay 100p in the £ (and there is no requirement for you to pay statutory interest) then no variation would be necessary.
I am sure that any confusion regarding this matter can be easily resolved and so I look forward to hearing from you.
Very few IVAs these days provide for statutory interest to be payable in the event of a return of 100p, so I would check with your own IP to see if you have this provision before getting too caught up in that issue.