Boiler broken! How can I help keep puppy warm?

As the title says our boiler has decided to go kaput in -3 degree weather (Celsius) and won’t be fixed for another few days. Does anyone have any recommendations on how to keep puppy warm overnight?

He’s a 9 month old black working lab mix and has quite a thin coat. Along with a heavy dose of steroids that he’s on for meningitis he’s lost a bit of muscle mass so can’t bear him to be cold!

He sleeps in a crate overnight with a cover so I’ve put a thick blanket over the top of the cover to keep I’m some warmth, I’ve put two extra blankets in there and warmed up some hot water bottles which I’ve put in there. I’ll take them out before he goes to bed!

Does anyone have any other suggestions?