Stop press! I collected everything this morning. Because it had all been frozen at low humidity, and because it's still below freezing here today, we were able to open the mutton boxes and write "mutton" on all the labels with a sharpie. Nice and simple, and hopefully foolproof!!
It's such a relief to have everything 'safely gathered in', so I can now get it out to people before Christmas and I certainly won't be leaving it this late again.
Thanks for your help everybody!