What/How would you do it

[acaciaguy]

What about having a 45 - 45 joint across the corner ? Drawing a line from corner of window frame to corner edge of sill ? Ie. Bending tiles around the flat sill corner?

 

[Flintstone]

Here's one I have just done . Different tiles and situation but same principle.

 

[acaciaguy]

That looks great. I think it would work in this situation but I guess it’s personal look etc

 

[andy holland]

That looks superb but I'm still left with the small cut which would have to move to the bottom of the picture which is the front edge and you dont put cuts at the front so, I think my only option is to return the tiles and buy larger ones...
Genuinely, thank you for taking the time in replying, as well as larger tiles I'll also buy some different curtains.