Thanks for the good advice. I agree they don't look quite right as dense as they are. There will be diagonal cuts for the fall to the shower drain so I’ve tried to hide these grout lines in dark areas of tile, eg top right. The same goes for the radiator pipes-thought they’d look better poking through a dark area of a tile. But don‘t think it works as it is. I’ll have another go.

Hey! Yes, you can put a rug anywhere, but in this case, another kind of rug will suit, better. You can consider a single colour rug or up to 3-4 colours to match your bathroom style.

Got a picture

You usually start in the middle and work out towards the edges. This does require more cuts as both ends usually need to be cut. I assume you are talking behind the bath? Another option is to start with a full tile in the innermost corner and work out. Get the dimesions of the bath and work it out with the size of your tiles. Your tiler should have some ideas but don't let them take the easy way out. You have to like the finished job and live with it. If there is not an obvious way to go then sometimes it is down to individual preference. If you use the factory edge in the corner then you know it is straight.