Hi, got mine from maplin ( HEF 4051 BP ).
At first I tried to follow your pictures and the tutorial but I was confused.
Your pictures relate to the right hand diagram from the tutorial ( logic symbol ). That's what confused me.
I followed the left hand diagram ( pin configuration ) and only the tutorial and now it works like a charm.
Obviously I had to had a analogueRead to read the thing. I think all your trouble scared me

Daniel:
I don't understand why the tutorial as a beginSerial instead of the Serial.begin. Is it because of a old version, or the code is for wiring?
And I didn't use any capacitor.
Tomorrow I will try to adapt the capacitive thing to the multiplex.
Do you think that one of us should do a simple tutorial with pictures on how to wire a multiplex and rewrite the code so it actually do something when the arduino is wired properly. I am happy to do it, but I won't do it directly as I have lot of work. I still don't know what pin 6 and 7 (E and Vee) are for, ground access ?