A traditional flat loses around 20% of its heat through draughty doors, windows and uncontrolled ventilation gaps, such as chimney flues.
Look out for spider webs to locate draughts!
An open fire loses 80% of the heat up the chimney: if not in use, be sure the flue is closed and glass doors (which require LBC) are in place to minimise heat loss, always ensuring it is well ventilated. Consider a chimney pillow/balloon, an inflatable bag made from a special laminate that makes it airtight and which will shrivel up if heated by accident.
Rooms where water vapour is plentiful (eg bathroom, kitchen) and rooms with gas-fires/appliances should not be draught-proofed unless means of ventilation is available from a ventilator or window.
Traditional buildings were designed to let air circulate between the outside and inside of a building. Sealing up the building too drastically may lead to problems of damp, mould and timber decay.
This is easy to do yourself and will not affect the visual appearance of your historic home or damage its fabric.
You can save about 170kg of carbon dioxide (CO2) and around 60kg of CO2 with pipe insulation.