Sorry tatty but your DP's anguish made me laugh a bit! We are also at MIL's. The length of nap comment thing is hilarious. My DM did it for both of my sister's babies and for my own, and MIL did it for all of her grandkids too. They really truly honestly forget what babies do at different stages, as in the short nap being a thing at this age, not to mention the fact that babies usually don't sleep as well in strange houses.
DM has had 5 babies, and admits it's all a blur and she doesn't know how the hell she did it.
DH and I are going to reclaim the cot (currently in use as dd1's toddler bed) when we get back and set it up for the baby in our room and maybe start gradually sleeping in the spare room in a few weeks. We are definitely keeping her awake when we go to bed and that's frustrating.
Our Co sleeper cot has not been a medium success. Very handy to put the sleepyhead in initially, and great not to have to move on cold winter nights, but she's so close she wakes at the slightest movement or cough which is maddening.