Do wood burning stoves need a chimney liner?
Since 1965 British building regulations part J require all chimneys to be constructed with a suitable liner, However, most of these liners are large clay pot liners, designed for open gas or solid fuel fire. Although theoretically, this type of liner would be suitable for a closed appliance like a stove, they are most commonly 200mm diameter and it can be very difficult to build in a suitable sweep access. Even if this could be achieved the chimney would still need to be tested first (and by this I don't mean light a smoke bomb and see if it comes out the top).
To correctly test a chimney as described in building regulation part j appendix E3, first the chimney needs to be swept, the existing flue liner and sweeping debris examined for signs of damage to the original chimney lining, then the chimney should be capped off at the top and bottom and pressure tested. Done correctly this can take over an hour and would generally need two men as it involves getting on the roof so expect to pay around £100-£150 just for the test!
After this is done, and you if find it is possible to build in suitable sweeping access for your appliance you can install a stove without relining the chimney.
However, after the install, you could now find that you have a problem with your stove!
High-efficiency stoves are not designed to work on large flues over 175mm many will burn two fierce if the chimney draw is too strong and this will reduce the heat output and could damage your new stove.
What about old brick built chimneys?
Old brick built chimneys (pre-1965) were lined with a mortar screed as the chimney was built, this system of lining usually last around 30 years, so it is very unlikely to still be in good condition unless it has previously relined.
In fact, in the last 25 years, I have only seen one original brick built chimney with its original lining still intact and in good condition, It was in an attic room and the only reason it was still in good condition was that it had never been used.