If you can feel a draught from your windows, chimney, and doors, then you can bet energy is seeping out of them. A cheap solution is to use draught excluders. You could also hang thick, substantial curtains rather blinds.
A more expensive but longer-term fix to save energy is to replace single-glazed windows with double-glazed windows. If you find UPVC windows ugly, then pay the extra for wood-framed windows. It's not just an aesthetic factor, as they provide more insulation, cause less pollution, and are easier to repair.