Dave

Hi there...that gear the walls are skimmed in is as porous as hell, prime the walls with a watered solution give it 3 or 4 coats to cut down on its moisture sucking properties,might need more coats...then tile with bal single part flexi adhesive this is slow setting so will give you plenty of time to play with the tiles and lasts in the bucket for ages and sets on the wall in about 16hrs..this should work for your project no probs and grout with flexi grout with those porcelain tiles...........dave..