If you are starting off with half a tile from the work-surface then make sure you are starting at the lowest point so that you are nipping the tiles on the higher point to keep the setout level else starting off at the higher end of the worktop would cause you to have a gap at the lowest to stay level or you'd follow the drop/fall and wouldn't be level.
Not too sure on charges. If it will take you a day then it sounds like you're on a fair wage charging what you quoted so i'd stick with that.
I'm sure the others will give their view in a bit, most are at work at the moment.
