Wood Burning Stove Problem

[here3ring]

Need some advice on what to do when installing a wood burning stove into an existing fireplace.
My problem is - Do I need to insert a liner into the existing chimney?

I have a large masonry fireplace similar to an inglenook fireplace in which we currently have an open fire (very inefficient).

The opening at the bottom is 1.7 metres x .58 metres.
This tapers up to a rectangle of 153mm x 350mm
At this point there is a lined rectangular box of this size all the way to the top of the chimney.

Would this be sufficient to be used for the flue to be inserted - the flue being circular or would it need to be lined with a circular lining that the flue fits into?

If so does the current lining need to be filled out when the circular lining is fitted?

If not then can the flue just sit within the opening of the existing rectangular lining?

Many thanks for any advice that may be forthcoming.

[htg engineer]

Normally you would just connect to a brick chimney.

When you buy the stove, it'll tell you the type and dimensions of flue you should use.

http://www.fluesystems.com/liners/

htg