Bod! :lol:
Yes, you can
tile onto
cement backer boards. These need to be fixed to the wall with flexible
tile adhesive and screws/rawl plugs. But it may be much easier to make the render flat and
tile directly onto that (can't say 100% without seeing it, but understand that your camera doesn't work at the mo, Flo :smilewinkgrin
.
You can either re-render with sand and
cement (you can buy 20kg bags with the correct ratio of sand to
cement, they should only be a fiver, or less), but expect to make a fair old mess, because render is thick and at least half will fall on the floor.
OR, you could do the same thing but with a flexible
tile adhesive, which is much easier to work with. Just make sure that you don't exceed the maximum manufacturer recommended thickness. Stonefix adhesive from memory allows up to 20mm, which is one of the higher thicknesses. You would use the same adhesive to fix the tiles.
This doesn't help you, but local to me they are selling 300 x 300 black galaxy granite for £18 / m2. That would look nice in any fireplace and would be the perfect material and colour for that application. If they are £18/m2 in Sweden then you MUST be able to find them for that price, or less, in the U.K....
Good luck Flo