In reply to sweenyt: In general, with 3 people, if the first or last person falls in you don't bother messing around, the other two just put some effort in and pull them straight out.
If that doesn't work, then the middle person just holds the one who has fallen. The end person moves forward, puts in an anchor slightly in front of the middle man and takes the weight off the rope. The middle man then unties and you proceed as normal.
If the middle man falls in, you just treat it the same as for a pair. The third man just drops coils if required and you sort things out once the middle man has been rescued.
As regards the prusik on the rope, I have never seen the point as you still need to unclip it from your harness and reconnect it elsewhere either when hauling or ascending. However, they idea is that it just saves the hassle of trying to retrieve a prusik loop from somewhere awkward like the back of your harness and then attached it with the correct number of turns when you are in a precarious position.
HTH