I wondered what peoples thoughts were on placing a plasma tv above a real fire place?

We are building a new house and looking at various set ups, but looking at the basics of the lounge, the best place for the TV would be over the fire place.

Do we need to add extra insulation if we are fixing the TV to the wall and cables will be pre-wired above the mantle piece (coax / cat6).

Would it be better to have the TV off the wall and fix with ceiling mount?

Not concerned at this stage about the tv being too high / low / wrong angle and any thoughts would be appreciated.

Many thanks.