Regards the washing machine, your exit hole can be as low as you want, but I would leave space for even a shallow u-bend, that'll stop the spiders invading the house. the trick is that the overflow hose must be in a stand pipe that is higher than the wash m/c drum (about 6" or 150mm under standard work top height) otherwise water will always run out// wash m/c never fill.
Sink :- Are cupboards already fitted and a straight through the wall exit required? If so drop sink in, put U bend lightly in place from the bottom in mid position (there's a bit of play) point open end at wall, draw round it, remove, theres your centre, dishwasher will be ok on this but as a preference I'd keep the wash m/c seperate.
As for the holes, you could use something like these
http://www.screwfix.com/app/sfd/cat/cat.jsp?ts=82089&id=101719 or as I did, used a normal hole cutter to break the outer edges of the outside bricks (after drilling a centre hole through the wall from inside) and then use a normal (long) masonry drill, gives a nice finish to the outside appearance.
Pipes should when going through the wall tip "down" slightly to aid run out, if they point up you might find your baked bean remnants from sink or your collection of blue belly button fluff from wash m/c may not flow out and collect in the trap.
Basically if it all goes downhill water will run away with it.
