'Handing the keys back' - voluntary repossesion/shared ownership.

CapJ

You haven't said why you can't alter the price of the property. There are normally two reasons for this. 1. Partner isn't willing to accept drop in price. If this is the case you need to make it clear to your partner the alternative is having it repossessed (or handing back the keys - little difference). This would result in a default in the credit file and you both oweing more money.

The other reason could be that you have reduced the house to the current value of the mortgage. You should contact your bank to see if they will allow a below mortgage value sale. Many do, and they may even be willing to help sell it (it is in their interest after all). You will both need to sign an agreement to pay the shortfall. Realistically, it would be better to do this before entering into and IVA.

Edit: A third reason I had forgotten about is linked to shared ownership, especially housing associations. Realistically they tend to lose out in below market repossessed sale so if they are holding up the process you need to be frank with them and see if they will help. They also might be willing to exceptionally let you rent it out.

In any case you should post more information if you want helpful replies as it is a bit of a guessing game at the moment.