Our heating is set to 15 over night, 21 during the day. We have a Tado thermostat and switches off if I leave the house automatically.
If it produces heat, or cools, it uses a lot of electricity (so heaters, freezers, etc.). Don't worry too much about other devices on standby, anything in the last decade or so won't use very much just on standby. You're probably talking a couple of quid a year. There's been a lot of scaremongering articles lately about electricity usage on stand-by, but they get the figures wrong by a factor of 10 or more.
Devices will use a few more watts if they maintain a network connection to check for updates etc. (Games consoles, smart TV's etc.) but it's not a lot, and there should be options to turn that off.
Replaced the seals on our Windows last year, that made a big difference to heating, they were quite drafty!
Our combined bill just went up to £175 a month, two bedroom house, two fish tanks, two freezers, two home servers, lots of smart home devices on all the time.