"We'll improvise, then," he says. "These places tend to be fairly cookiecutter."

He doubts the Trunchbull will have chosen anywhere especially fancy.

"You handle Miss Trunchbull, I'll stay out of her sight and get Jenny out."

This is not the plan he would have chosen an hour ago, but an hour ago they didn't know she had powers of her own. Matilda has a chance at defending herself against them; Jim does not. Best for the Trunchbull to think Matilda is on her own. Jim will only be a liability if she finds out about him.