Tiling around a wall mounted electic fire

Hello all I'm hoping to tile around and fit an electric fire to my living room wall before Christmas.

What I plan to do is fix the electric fire to a 4ft x 2ft MDF board using the bracket provided. I then want to tile around the electric fire with split face slate tiles. Finally the whole thing would be attached to the living room wall.

I don't really want to hang the fire on the wall and tile as I would like to move the whole lot easily in the future.

My question is what would the be the best material to tile onto?

I understand MDF isn't suitable for tiling but will provide some rigidity. I was thinking either fixing plasterboard or Hardiebacker to the MDF.

Which adhesive would be best?

No grout will be needed but i want to treat the tiles to bring out the colour.

Would this be done before or after tiling?

P.S The electric fire will not be used to heat the room, it is purely decorative.

Any help, suggestions and advise would be appreciated.

Thanks