Thanks for the advice. Sorry to hear about your bun Oreo, but glad Pandora has a new friend now. It's also good to hear introducing a new bun into another's territory can work well.

It's been over 12 hours now without fights/scuffles (tiny bit of nipping/chasing, but otherwise fine) and they've been on their own in the kitchen for a couple of hours without any problems. They're currently sat snuggled side by side, so I think they're ready I'm in the process of cleaning the shed now, so we will try putting them in there together in a couple of hours, wish them luck!