Indoor buns going outside?

Hello all! So we picked up our giant contis 6 weeks ago, with the plan of them being house buns. Bobby (our boy) has cottoned on straightaway and is the perfect house bun. Bella (our girl) doesn’t seem to be as happy though. She’s not really got the litter training, and is very destructive. We’ve obviously bunny proofed but it’s not wires etc, she will literally pull up the wooden flooring and she’s chewed two holes in the sofa, plus she always wees and poohs on the sofa every time she’s out. I feel bad as the plan by now was for them to be free roaming, and it would be Ok if it was just Bobby, but we can’t trust Bella. I knew there would be a certain amount of chewing but it’s getting to the point we won’t get our deposit back when we move. They have a large area sectioned off but it was only meant to be temporary and it’s not really big enough long term. They are only 3.5 months old, so the plan is to try again as house buns once neutered etc, (which is booked for this month) but in the mean time I’ve converted our large unused shed to be a bunny house. My only concern is that although they were outside when we got them, they’ve been indoors for 6 weeks. I’ve been leaving the windows open in there room for them to acclimate to not having central heating but I’m really concerned about it being too cold outside, but they Will have so much more room. I’ve bought some of those oat heat bag things to put in at night, and they’ve got an insulated box with loads of hay and straw to sleep in, and of course themselves to cuddle up to. Will they be ok??