First winter heating bill — is it just me or are these houses not built for cold?

We've just had our first proper winter in Australia and the electricity bill arrived this week. I opened it twice to make sure I was reading it right.

Some context: back in Lahore the problem was always heat, never cold, so I honestly did not think about heating when we chose this house. It's a nice place, but the windows are single glazed, there's a gap under the back door you could post a letter through, and the heating is two split-system units that seem to run all evening just to keep the living room bearable. The kids sleep in hoodies. My wife has started calling the hallway "the fridge".

I know the obvious answers are to use less and wear more, and we are doing both. What I'm really asking is:

• did your first winter bill surprise you like this, or did we just pick a badly insulated house?
• what small fixes actually made a difference for renters (we can't replace windows)?
• does it make sense to ask the landlord for anything, or is that pushing it in year one?

Also curious to hear from people in Europe heading into winter now. Maybe we can save you the shock.