Looking good Robin.

In order to move a pivot you need to select the group or object, hit w to activate the movement manipulator, press insert and move the manipulator, press insert again once you have the manipulator where you want it.

There are various snapping methods....

Snap to grid = x
Snap to curve = c
Snap to vert = v

While the manipulator is in the insert mode hold the cursor over the vert, grid point or curve that you want to snap it to and holding down the relevant key (X,C or V) press the middle mouse button, hey presto snapped to point!

you can move objects in this way too by snapping while out of the insert mode.

Take it easy,

Mat.