We have a 1930's tiled fireplace in the house we are doing up which needs replacement, and I have ordered a cast iron surround ('inset'), fireback and wooden mantel which I was thinking of putting in myself, and then getting a corgi registered gasfitter to test the flue and  connect a gas fire.

I am aware of how to install a standard fireplace, form a throat etc.  but have never tried to fit a cast one before.

Currently there is just a large square hole in the chimney breast - a concrete former surrounded by rubble and cement - where a back boiler once sat.

Is the job as simple as creating a channel for a gas feed, installing the fireback and filling the gap with rubble and cement?   Are there any difference between fitting a cast iron fireback and a 'normal' one which I should be aware of, like it needing an insulated jacket of some sort? I seem to remember seeing one which had been recently taken out which had such a jacket.  

Lastly, do I cement the cast surround in completely or should it be allowed room for expansion?

Many thanks

John Davies