Chimney Liners

The open fireplace in our dining room was used recently to burn some papers.
We could smell the smoke in the bedroom above this room and I assume that the pargetting inside the flue is defective (the house is about 50 years old).
In order to avoid the problem in future I think that what is required is a chimney liner, but I have no idea about how to set about this job.
Iwould be grateful for any advice on such things as:

How do you seal round the liner at the firplace opening in order to prevent smoke from bypassing the liner?

Any notion on cost of buying the liner and fitting it, bearing in mind that my wife is now rather too old to be climbing on the roof and that we will have to pay someone to do the job.

Any other info.

Thanks in advance.

BillK

A relative had the lining replaced recently in a house of similar vintage. The problem had caused smoke damage in the house this past winter. He got a large portion of the cost covered by his home insurance and it ran to thousands rather than hundreds. The labour was 3 guys for 2 days.

I had a chimney fire in a rented property during the week and the fire men told me that there is a crack in the chimeny up in the attic. There are no flue liners in the chimney just 3 No at the top where someone had rebuilt the chimney some years ago. The house is over 100 yrs old (a single storey stone cottage).

An elderly lady has it rented from me and lights the fire early in the morning and it is lighting all day, she burns coal and timber and it has a backboiler - what is best to have the chimney lined with? Traditional Flue Liners or Double Skinned Flex and backfilled with microfil?