By the way, sorry if I state the obvious, but when I said turn off the water, I ment turn it off at the mains, or the tank, not the taps themselves.
Another trick is to leave another tap running after you turn off the water as there is normally a small trickle past the tap. If you have them, use blanks to close off the pipes as they might be open for a few days, depending on the tiler.
And (sorry for the stream of consciousness), it may be possible to just undoo the screws holding the cistern and sink to the wall and move them out a few inches. Be sure you can support them sufficiently in this position. This might give the tiler enough space to put in the tiles and you don't have to undo the taps/cistern feed at all. This of course depends on the type of cistern (close coupled or not, and sink (pedistal or not))
hope it helps.