If you sell the house the equity will be due to the IVA anyway. You could offer to sell for the purposes of ending the IVA early --- basically saying " I will sell the house in order to be able to give you £xxx, as a full and final offer to close the IVA early. If the offer is rejected I will not sell".
Alternatively, and probably better, speak to either Ryan or Shaun, who are both whole of market brokers. I know that Shaun has access to products allowing equity to be used for an early exit, and I imagine Ryan might do as well.
Their contact details can be gleaned from their profile pages here: