Where to start tiling

[rotadays]

Hello everyone
Really appreciate some advice.
I have a small en-suite approx. 6' 6'' square immediately to the left as you walk in through the door is the window approx 3' 6'' x 4' other than that featureless a square room. It has all been re plastered and basically a shell
I have looked on here at previous posts and I realise all rooms are different but it makes sense to me to start around the window as no bath just a shower cubicle and tray, toilet and sink vanity unit to be fitted, the 600mmx 300mm tiles will be layed linear pattern.
So I would really like some advice on how do I find the starting point for that perfect window tiling job.

 

[alan333]

Figure out how you're doing all the cuts. For example if your walls are 6 feet 6, and your tiles are 2 feet, you could have a 6 inch end cut on every wall, or you could have a 3 inch cut at each end, or you could start with a half tile and end with a two-thirds tile at the other end. It would look more balanced if you started and ended with the same size cut, ie a 'foot and a quarter' tile at each end and two full tiles in the middle makes up your 6 feet 6 (this is how I'd do it but you'll use more tiles).

Figure out your window wall in the same manner, ie how to make the cuts look symmetric and even.

 

[rotadays]

Thanks for the advice, I can honestly say respect to pro tilers who pretty much sort out the tiling straight away, I have been trying different scenarios most of the afternoon, just when I think I have cracked it I spot a problem so could one of you kind gents or ladies just help me out with my final head scratcher.
I have fitted the waste for the sink and shower tray and water tested all good. I have researched on this forum and it seems some suggest tile first then silicone the shower tray, what I have decided to do is silicone the shower tray in now onto the moisture board then tile onto the shower tray, leave a 1 or 2mm gap then silicone between shower tray and bottom tile. I then thought about the cubicle which will be screwed into the tiles, one side block work the other dry lined.
Tiles 600x300mm layed linear pattern

My dilemma's questions

My shower cubicle is in the corner of the room 900mmx900mm taking everything into consideration with continuity of grout lines and trying to make the window tiles line up ok I have come to a first row which will sit approx 10cm above the shower tray, height of shower tray 11cm,total of 21cm to floor, leaving a tile depth of similar height at the top of the wall . As I have big tiles would a 10cm tile onto the tray look ok ? unfortunately I can't tile directly on top of the shower tray as the grout line runs through the radiator tails and so preventing me to be able to batten the window wall along the grout line.
Should I try to position the horizontal position of the tiles in the shower cubicle so when I come to screw the shower cubicle to the tiles I have a decent amount of tile to screw into.
Finally hope I haven't bored you to death yet, what is the best way to shape the cut of the last tiles around the shower tray, the ones which the shower plinth will fit against?
Here's hoping for some advice
Thanks