Hi. I intend to re tile my kitchen and have pulled off the old tiles which shows the wall still has the dried adhesive and uneven surface (pic attached). I'm just after some advice as to the best way to prepare the surface for new tiles. is it a case of completely re plastering the old wall to provide a complwtely smooth surface to grout etc and tile on a new smooth surface. Or can new tiles be layed on the surface as it is? any suggestions would be greatly appreciated.