this is what i make of it, you say you tiled from left to right tiling the left colum first then when youve done the colum of tiles directly above the door and the tiles have slipped on the right side then youve carried this mistake on in the next colum and by then its 150mm out of whack. what i would do is rip out everything above the door, replace that shortened tile with a full sized one and then tile the row above that which will be the two L shaped ones either side of the door and the slither directly above and centre of the door, tile these three making sure all the lines match up, the joints either side of the slither may be a little crooked but when grouted it will look a million times better than what you have now, then tile above it. jobs a gooden.