I guess I thought I wanted my nuclear family together for Xmas and was then including my mum (who I thought should be with us as she’s on her own) so felt like the obvious people to use overspill space was my MIL and SIL
I think this makes it even clearer, tbh, that they should be offended.
How can you suggest that your mother is part of your "nuclear family" but your dh's mother isn't ? 
I mean, full credit to your replies on this thread - you are being very gracious in accepting you might be in the wrong here, but that is very strange thinking. Surely both women are equal grandmothers to your dc ?
In terms of general discussion in the Autumn though, as they only live 40mins away then I don't think you would have been unreasonable to say "We are happy to have everyone here for Christmas day and boxing day as we have the bigger living room , but feel it is going to be too much putting everyone up as well, so are you happy to drive over each day or there is an Air B'nB a few houses down if you'd rather be able to drink, which I can ask about if you like ?"
I was presuming that they needed to stay. (Lived 100 miles + away)
We've been to a few different places over the Christmas period and it wouldn't occur to me to expect anyone to put us up when we were under an hour away. If we weren't prepared to not drink for a day then that is our issue, and up to us to find an alternative, tbh.