On Friday, 31 May 2019 09:53:56 UTC+1, Grumps wrote:
I am putting in a new (eBay) fireplace wooden surround and will need a
panel of some sort to cover the mess that was originally there
(wallpaper with bits missing, and a hole for a gas fire flue).

Modern electric 'fires' are usually fan heaters, so don't get very hot at all, unlike the old radiant bars.

The fire surrounds themselves are usually made of chipboard or MDF.

I would think that ordinary p/board would be sufficient.

Owain