<<Although my compass heading is now saying north It is actually pointing 2 degrees to the west of north.
Therefore I must add these 2 degrees on to my compass heading
to get true magnetic.>>
No, if your compass reads North and it is pointing to the west of mag N. then you must takeaway 2 degrees to get mag hdg!
If CompNorth datum is to the left of MagNorth datum by 2 degrees, you use up 2 degrees of your Compheading before you reach the zero of Mag North.