Good post. Ours have lived in the garage until this year, and I spent hours last winter packing hay round the pigs and down the backs of the hutches, covering the hutches with heavy blankets, picking out all the damp hay every night.
They stayed well all winter, but we've now brought them indoors (didn't think we had room, wish we'd tried it before) because one of them was very ill in the autumn (he has since died) and had to come in, so the other two came too. They are getting on a bit now, and I even before one of them started to fade, I was concerned that they might find it harder than ever this year.
I know it's not possible for everyone, but it's better for all of us now; the pigs are warm, they watch lots of telly and get loads of attention, and I don't have to worry about them or go out in the cold myself to look after them.