If you are renovating, take care, the larger the tiles, the harder it is to keep them even if floors and walls are not 100% smooth. This can lead to tiles having a "stepped" effect. As far as 600 v 300 look at cuts, and what will fit in the best. Unless your bathroom is very large, I would be concerned the 600 could be overpowering. I am more concerned about you using a matt tile, have you experienced them before?? I found them very difficult to clean and keep clean, every spot of water and finger mark shows on them.

Thank you very much for your comments. I have used matt tiles before but they did have a slight glaze and they work really well. My reason for choosing matt is that I have found that gloss tiles show all the dried water marks. My concern over the large size on the walls is a visual one. The floor I have used large before and they look great and there is less grout to get discoloured over time. The bathroom is not large.

Yes, I do understand about the water marks, that was the problem I had with my old matt tiles but my new high gloss tiles don't show it strangely enough. They do have a slight pattern in them that might help.

The visual aspect does concern me too, especially with them being plain white and if the bathroom is not that large. With minimal grouting, could they end up looking a bit "plastic", like you lose the effect of them being tiles, if you know what I mean. I recently renovated my kitchen, and planned on having all white doors and drawer fronts, but my pantry cupboard had two sizeable panels that would look like wall and I felt by having them white, it would give the kitchen a "plastic" look and cheapen it. I ended up doing the doors and drawers in the same yellow as the walls, and am really pleased I did now as it is hard to tell what is wall and what is the side of the pantry and the other cupboards and drawers blend into the walls and make the kitchen look larger. I know that is not a good comparison, but white is not always an easy colour in some surfaces.

Looking at my 600 x 300 wall tiles, I really think I would stay with that size, there really isn't that much grout in that size anyway and I just think they will look classier.

Thanks for your feedback. We have chosen a travertine marble look alike for the floors. The white wall tiles are matt, but maybe not totally matt. I was worried about the "plastic" look if I used the large ones on the wall. I was hoping I might get someone make a comment who has done this already.

Oh, good I'm glad we are on the same wavelength. Hope you get some response, it is such a big decision to make. Good luck.