Continue tiling around the room
fixing the first rows of tiles in bays of about a metre square until these are complete.
You now have a solid foundation from which to build your tiling. Double check that the corners are not stepped and that the verticals between the tiles are staying vertical. It is surprisingly easy to run out of line.
Leave the batten at the bottom in place until the adhesive has fully set otherwise the tiles may slide out of line.
As you work, remove surplus adhesive.
Tiling around windows or basins
When the tiling goes above a window or basin, for example, fix a temporary batten to support the first whole row above the item rather than fixing the cut tiles first.
It is a lot easier to cut these tiles into place when the surrounding whole tiles have been fixed and have set.
Over a window, the cut tiles will have nothing underneath them to stop them sliding down the wall. Once positioned, use masking tape to attach them to a previously fixed tile to hold them in place until the adhesive dries.