Buying a New/Used Fireplace

[mylittlehouse]

Hello All
I need a little advice please

i went and looked at a few and i quite like the cast iron inserts.
i have found one by stovax and they are quite expensive

i am thinking of buying one on ebay same make.
is this a good idea it just needs a replacement firebrick.

does anyone know if cast iron inserts appear on ebay quite frequently?

Also when looking for a surround how do i know if it will fix my fireplace?

Thanks