Thank you Dr. Retro - yes re-tiling the shower base, but it is a good size with a lineal drain at the far end, so should be easier to slope than an old middle drain, shouldn't it? The room is 3.5m x 2.0m - shower is up one end and is 1.0m wide x 2.0m (Walk in one end, drain at the other).

I originally was going to use all 300x600 tiles, but there isn't enough - should i try and use all 600x600? The room is part of an extension, so all new walls, so there shouldn't be any reason the builder can't get them pretty flat/straight.

Thanks Dreamer - love the picture, that is sort of the look I'm going for! And good to know your sister did this and it's ok! Yes, i don't want any more grout lines they absolutely necessary :)