In 2008, house values were tumbling in the United Kingdom. But 2 weeks after my husband and I put our home of 40 years on the market, a buyer offered us a good price and we agreed to a sale. Soon our builders started work on the house I had inherited, which would be our new home. But a few days before the sale of our old home was finalized, our buyer pulled out. We were devastated. Now we owned two properties—one whose value was tumbling rapidly, and the other a virtual ruin that we could neither sell nor move into.…