I'll be tiling my bathroom (approx 15m2), can you tell me which is the
best
tile adhesive/grout.

For readymix, I've used various BAL products. For powder types, I've used
Ardex Arduflex. Both have been excellent. I always check that the product
claims suitability for commercial swimming pools and ensure that I use a
100% fill technique, taking off the occassional tile to ensure there were no
air gaps.

Christian.