Myles and Sophie both signed an agreement that said if Sophie can wait out a 90-day escrow while living at the castle, the sale will be completed and she'll own it.
When Sophie offers to let Myles continue to live there after the sale goes through, he's immediately angered and insulted that she'd think he'd want to live there as a guest.
But the sale is already close to going through, and if Sophie didn't offer this, he wouldn't have anywhere to stay.
Instead of reacting kindly, Myles taunts Sophie and says he wishes they never met, which is quite cruel and a sharp change from the happy moment the couple had minutes earlier.