Cold house question

Hello! Wondering what peoples experiences are of the best/most efficient Tado usage in cold houses. I am in a Victorian terrace, rooms have high ceilings, 3 floors & no insulated loft, large cellar below kitchen/lounge area. I went away for the weekend just gone and left the heating off, noticed on Sunday morning that some rooms had dropped as low as 9 degrees Celsius! Switched the heating on via Tado and it was on full all day and only reached about 16 by the time I got home. So last night figured I'd set it to not drop below 15 in the living room but since the house is so poor at retaining heat the system was just on/off all night (screenshot below)

This doesn't look very efficient and since the house is struggling to stay at 15 then could I in theory set it higher during the night and get the same pattern (as long as it was at a higher temp when I went to bed)? Boiler is ideal combi c30 which I don't think is the best but all rads are getting really hot. There are things I need to do to the house to improve the insulation (thicker curtains/ properly insulate between floorboards and cellar roof etc) but until I get round to doing them I'm interested to hear from any fellow Tado users who have old draughty properties and how they manage it!

Thanks!