Draught proofing your whole house can be quite expensive compared to the return on investment.
There are some easy areas though to reduce energy loss through draughts and bad insulation.
Some primary areas to examine are:
1. Chimney Draughts - The chimney can be a massive heat loss area but it can be easily filled with a chimney pillow.
2. Letter Box and Door Draughts - Again, an easy solution exists to reduce the draughts in these areas and still get your letters and open your door. Things have come a long way from just a sausage dog pillow by the door.
3. Floor Board Draughts - A variety of products exists on the market to fill these offending gaps in and it is simple work. See below for a product which accomplishes this via a floor filler. This will reduce draughts and also noise and light coming through these gaps.