I want to tile my shower room floor. Bought the ceramic tiles and Bal powder adhesive and grout. It is a solid floor and assumed the existing vinyl flooring was on concrete. However, I have found that under the vinyl is a thin (about 1-2mm) of some grey screed some of which came up with the vinyl. Under this are what look like Marley type tiles. If I clean up the Marley tiles can I lay my floor tiles directly onto the Marley tiles? Advice would be much appreciated.