Peter
The alternative is to tell the lender that you are handing back the keys and going to the UK.
However, if they wish, you will gladly put it on the market for them and give it three months to sell. In return, you want them to write off the shortfall.
I think that they will agree to you selling the house, but won't formally agree to writing off the shortfall.
However, when the new debt settlement legislation is brought in, you will be able to deal with the shortfall in a manageable way over 5 years.
Brendan