Lining the flue to install a wood burner - access to roof required?

Hi, I live in a flat which is in an large Victorian house which was build about 1880. It was converted into 9 flats about 1985. The flat is on the second floor, and there is a fireplace in the livingroom (flue is open). I would like to install a woodburner in this one, but I assume that I would need the flue lined. (is that always required?) The problem is that even though the flat is on the 2nd floor, the building is on a hillside and access to the roof is difficult, its very high, more like 4th floor. - to line the flue, will there be a scaffolding necessary, or can that be done by simply pushing the liner up from the inside of the flat?