Bubble wrap is pretty good for windows - anyone who has a greenhouse will probably know getting a UV-stabilised large-bubble (as against small-bubble like in jiffy bags) sheet works really well though of course you can't then see out very well.
www.twowests.co.uk/products/heatsheets?_pos=1&_sid=5aec2f81d&_ss=r
You can buy as much as you need by the metre together with clear tape to attach it... you can also get it from traditional garden centres.
I've been sticking it over all my worst windows and those that are in the bathroom as you don't need to see out of those... I also have very wide windows and thermal lined curtains make a major difference too. Leaving them closed will keep heat in.
Draft excluder strips - stick those around windows if they don't quite shut properly. If you never open the windows or don't think you need to open them overwinter, put gaffer tape over the cracks instead. (And use WD40 to get the horrible glue off in spring when you need to take it back off again!)
Night owl duvets double up as very cosy blankets for watching telly.
Watch telly on a tablet if you have one and if there's only one person watching - the viewing angle is similar if close up, but it costs a lot less to run.
Turn lights off while watching telly if you can! Makes it more like a cinema too ;)
Tiny hot water bottles! You can get three for £12 from Amazon... and tuck them round you if needed. I then use the water for plants or adding to the loo cistern which then saves me again.
I have in the past student house used the hairdryer+plastic sheet double glazing to stop leaks round a sash window. And also I've shoved a roll of cotton wool in a big gap and gaffer taped it in place to stop a howling gale...