Never bring them in. :) This is only my second year, but last year I did throw a blanket over some of the sprouts when the temps really dropped to way below freezing and we had snow. I just used an old wool blanket that I had kicking around the house and kept it folded up and sitting on the BBQ (under the patio roof) ready to use anytime that I needed it. I have several sprouted containers out there right now and we have had below freezing on a few nights. I am not far from you and am probably getting similar weather, but this year so far, I haven't covered them. I haven't removed the top of the container yet either....just because I was expecting this sort of thing. :)...last year I only covered the ones that had their container tops removed already.
try not to worry.....survival of the fittest and all that!
gg

Well, I got nervous waiting for a reply and "rescued" them. OOps. Only the ones that sprouted, I left all those that had not germinated yet outside.

I'll get them back out tommorow, the temp is coming up anyway, so it should not be a shock to them, also the back room they are in is not as warm as the rest of the house ;-)