just a thought , why not just cut hole in mdf n leave mirror their , n cut hole to a size of suitable tin lid or grille or sumat n make a feature or fit another mirror over it
Like when I repaired a leak above a ceiling then fitted a loft hatch to save sorting the ceiling. Open the hatch and see the underside of a flat roof
Lol. I only buy the cheapo saw blades. Have you seen the price of the Bosch ones!! To be fair mortar and render is pretty soft, unlike tiles or glass.
How is the panel fixed if you can undo it there is probably a gap ether side or it would of been really hard to put in scrape the grout out slide to one end so it clears the other pull out plane a bit off to put back in you can use a glass cutter on the mirror bit then and kibble it away. or hack saw blade on a handle (drywall type thing) down the tile to release it