I have an oil heater which works very well for me, but yes, it's expensive.
Alternatively, there'll be a nice double-glazing salesman round your house again soon. :)
If you don't already have double glazing, putting up temporary double glazing film like this is well worth the effort, as is tackling drafts with that foam or rubber strip stuff.
If you don't already have double glazing, putting up temporary double glazing film like this is well worth the effort, as is tackling drafts with that foam or rubber strip stuff.