The chimney sweep who swept our chimney last winter warned us he
couldn't do a proper job because the chimney is dog-legged, and needed a
soor door installing in the chimney breast to facilitate access to the
awkward bit of flue. and basically warned us against using the fire
until this was sorted out. So the tuit has been rounded...

Has anyone fitted one of these things? Here's an example:
http://www.ebay.co.uk/itm/120541433027
Doesn't look too complicated?
How do work out where to open up the chinney breast, though? We have a
cast-iron stove with doors in the fireplace, so you can't really see
anything up the chimney. Also, the fireplace is on a party-wall, so no
chance of doing it from outside.

Presumably you take out bricks over three courses, I'm guessing ideally
at the dog-leg or at least on the non-vertical section of flue? Do you
use normal mortar? Anything else I need to know?

Can it usually be done through the *side* of the chimney breast? I'm
guessing (again) the brickwork would be much thicker there?; although
cosmetically it would be preferable.

Thanks
David