If their heat ran dangerously low then, hygiene issues aside, I'd probably put them in cloth bags (same size ones go together,) line my bed with a plastic covering, and stick them all with me under a few layers of blankets.

Heat up some hot water bottles (using gas heaters/fireplace) and we'll all have a giant reptile slumber party.

I'd recruit family members into this too.

But this would only be a few hours/one day thing if it was in the winter. I'd have to figure out some other way if it lasted for longer than a day.