chimney liner for open fireplace with not very good chimney ?

Hello everybody, long time reader, 1st time poster

We have a beautiful open fireplace which over the last few months has been giving us some major issues.
After a while, the house begins to fill with smoke, initially I thought it may have been the height of the chimney, however I extended the chimney and it still smokes after a while.
We've also had the chimney cleaned.

It wasn't until a took a closer look at the inner walls of the chimney and noticed smoke was pouring out of the chimney wall straight into the room.
What's strange about this is that those bricks are the "outer" chimney, if you get on the roof and look down the chimney, it has the main centre cavity where you can see the fireplace below, but then on either side of it there are to cavities the run down along the side of the main chimney.
Which are the bricks you see in the picture.

My logical conclusion is that the inner chimney must have some mortar breaks or holes which is allowing the smoke to seep out into the outer cavity of the chimney then come into the room.

My question is, can I get a chimney liner for an open fireplace ?
Is there a requirement for a collector above the fire, like an upside down funnel, I forget what it's called.

We are considering just putting in a wood heater but would like to see if there is a cheaper alternative.
Wood is not an issue, we have an endless supply

Please excuse the terrible picture lol

Thanks for your time.


Here's the picture !

Thanks very much for all your responses.
We'll most likely go with the a new insert.