But main thing you have to think about is your windows. Maybe you got, old, wooden ones? They are looking really nice, likely, but it isn’t enough. When you will exchange it for any new, PCV pieces, you should be able to keep a lot of hot air inside of your house. You do not need to remove each piece at ones, you could do it in several steps, to avoid too many expenditures in one month. Another relevant case is your roof. If you will cover it with any fibreglass mesh, it could also keep your house a lot warmer during the winter, cause most of the air is going away trough it, probably.
Then, you may invest some of money in external wall insulation. It should be very huge cost, but it is worth it, more: external render facades. Within several years, costs of it will come back to you into the heating expenditures. Also, when you like, you could at the end make some interior insulation as well, exerting also fiberglass mesh – it is the best product for all this sort of works. But where you may buy all the materials? It is really easy, go to the closest building department. You will find there all the stuff you need, from screwdrivers to fibreglass mesh.
When you are afraid of cold season, because of giant expenditures for healing, there is a great solution. You have to organize an external wall insulation and replace vintage windows with PCV ones, you may also like: eps adhesive. It should help you to save a lot of cash, and it is nice for environment, because you will waste a lot less energy. And the finest season to start renovation like this is summer. So perhaps you may consider it?