ok you have removed the old fire suround and hearth, now you need to fix a cast iron suround, the ones I have come across may have or may not have fixing on them ,if the suround does not have fixings on it you may need to drill fixing holes top and bottom each side, this is important as the cast iron suround is very heavy and needs a solid fix, if your fire place is active you will need to seal this suround to stop the effects of heat and smoke on your chimney breast, you can use fire retardent cord of fire cement around the surounds perimeter before securely fixing to the breast, then it's just a cast of fixing the wooden mantle with fixing lugs that should already be on the mantle istelf, hope this helps.
john, January 2008