@ICRag you will find lots of helpful advice on keeping warm this thread ( linked below ) . So many sitters said they loved heated blankets , with some bring their own to sits. There are lots of other helpful suggestions for sitters keeping warm in colder climates .( Like hot water bottles , extra layers, Co sleeping with the pets and baked potatoes 
)
So that future sitters know about the situation. You could write in your review that the heating is controlled by the landlady and is not turned on unless temperature drops below 16degrees and that the host has provide you with a heated blanket .