Removing unused gas fire flue liner (no chimney stack)

[damyan24]

I recently moved house and have this hideous steel / aluminium liner going through one of the bedrooms. There is a gas fire in the living room below which I'm not planning to use and getting it disconnected by a gas engineer and there is a steel chimney flue on the roof.

I have 2 questions where I would really appreciate some advice:

1. What is the best way to remove the flue and seal it without removing the chimney itself (so the room can be plastered in the next week or so)? Eventually I will probably take off the chimney itself too and make good but it's not a priority at the moment
2. Can I remove this before the gas fire is disconnected if I am not going to use it?

Thanks for your help

 

[cross thread]

It should stay till fire capped off,it will come out easy enough it’s only a twist fit after tape removed.better removing completely as it will probably rain in slightly through the terminal