Given that you will need to cut the tiles up to the ceiling anyway, there is no advantage in tiling first. Put the coving on and then tile, most coving adhesives do not work as well on a ceramic (glazed) surface. See the DIY projects section for help with cutting ceramic tiles.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!