Pesme - we do!
We have 2 - one in dd's room and one in ours. Didn't cost as much as I thought - certainly much less than having them properly blocked. our local chimney sweep/repairs company measured and fitted them, but I can see we could probably have done it ourselves.
We wanted to leave the chimneys open - our heating works with a back boiler behind the fire in the lounge, so on cold days we may yet need the extra fires!