I'd keep them somewhere very cool inside. I've left the new dahlia tubers in my car for tonight, but shall remove them before tomorrow evening, when the temperature will drop like a stone again, apparently. I shall be finding somewhere cool indoors to keep them instead (not easy inside, is it, really).

I agree with all of that. And don't plant them yet, it's too early.

THANKS GUYS! WHEN SHOULD I PLANT THEM OUT? I'S GOING TO BE DIFFICULT FINDING SOMEWHERE COOL IN THIS HOUSE!

Frost free garden shed? Put them in a plastic container with a few air holes to protect from mice.

or you could plant them in pots of compost and keep them in a shed/frost free garage then plant out in April/May.

THANKS FOR THE IDEAS I'LL LET YOU KNOW HOW I GET ON.

I would do as seaburngirl suggests - pot them in dryish compost, as you would a dahlia, and keep them cool, until the time for planting comes.