Sorry to hear about your MIL Rufus, hope the DC are coping OK, and you and your DH. We lost my mum 18mths ago, DS was in the room when we got the call, DD we told next morning, she was the most emotional. It was expected, mum had cancer and we knew when we spent xmas with her 7wks previously that she wouldnt last long into new Year. She went into a home on NYE and had just celebrated her 90th a week before she died. We all thought she hung on for the big birthday then let herself go. I was relieved it hadn't happened in the middle of the kids doing GCSEs/A levels in the June.
In terms of double duvets, DS room last year was in a 2 yr old hall and was baking hot!! I think the only time he didnt have the window open was in depths of winter. He definitely only needed a thin duvet. Think this year could be a shock for him and his halls friends, moving into shared houses!!!!!