I live in a drafty old house. Single skin walls, wooden floors etc. I had a leaflet from the council saying you could save up to £70 by blocking disused fireplace chimneys. We have one in the lounge and one in the dining room.
I bit of research later, I found out about chimney balloons and chimney sheep and set about watching Youtube videos on these and looking at reviews. Chimney balloons are about £15 and are supposed to be pretty useless according to the reviews. Chimney sheep, for our size chimney £53 each and suppose to be very good.
I came over to mumsnet and found a thread about using neither! Just pop upstairs and find the mankiest pillows. Pop one in a heavy duty black bin liner and stuff it up the chimney ensuring no gaps! People have said that it works a treat and that it makes a big difference. Thank you mumsnet!
(DS now has 2 new pillows for his bed too. Total cost £10.50 for 2 blocked up chimneys)