I guess I'm fairly committed now to doing mine at least!
https://dl.dropboxusercontent.com/u/2793861/2013-05-02 12.37.19.jpg
https://dl.dropboxusercontent.com/u/2793861/2013-05-02 12.37.19.jpg
Looks good to me
Don't Panic! The corner trims work from only one side so you can buy a trim, tack it onto the window ledge and around the window then tile onto it.
But all the videos i have seen show it being placed on the front facing tiles? also the trims i have only have a small piece of lip to cover the front facing tiles if that makes sense
I have done it both ways, used this from Wickes http://www.wickes.co.uk/invt/166084
I just bed it in on the window still & then tiled over it, from your photo you shouldn't have any problem, might need to trim the plaster so it sits flush with exsisting tiles.
make sure you have adhesive on those tiles already there to ensure good bond when you bed the trim, & to have water resistant seal.