Thanks for your feedbak, Tatyana! I wish you would've mentioned your discomfort with sleeping at floor level when I showed you the apartment: the "mattress" is a part of the sofa that can be lifted up and attached to the sofa to form a second double bed. Since the people on the sofa weren't a couple I figured they would be more comfortable in their own beds. It's such a shame you had a bad experience with something that could've been fixed so easily.
As for the heating, everyone is of course always free to adjust the heating to any level they feel most comfortable in.