Some people say that there is an increased risk of the bun developing snuffles and other respiratory problems if brought indoors. Personally, I take this risk with my buns because otherwise I'd never spend any time with them in the winter and they are my pets and I need to be with them. The only bun I've ever had which has got snuffles is Widget, one of my new buns, but my vet said some buns do harbour it more than others. I never had any problems with any of my other buns bringing them in most evenings in the winter time so I believe the risk is low. Widget has been treated and the vet believes there is no need to continue her treatment even though we're keeping a close eye on her in case she worsens. But she seems stable.
Personally.... at 4 degrees.. I would ...
Off i go to fetch him- he will be happy bless him
It's a tricky one isn't it - what sort of temperature is it in your house? I feel cold at about 15 degrees, so there could still be a big differential between inside and outside.
For me it's not so much whether bringing them in will make them ill (although of course that's a consideration) it's more a matter of kindness. I wouldn't like to come into a warm house for a few hours and then be popped back outside in the cold without an extra coat. Even if it didn't make me ill, I don't think it would be very nice, so I personally would only do it if the heating is off and the room is genuinely not very different in temperature to outdoors. If there's a big difference, I wouldn't do it, because it would be exactly like me going outside in my pyjamas having been indoors for a while.