318 is coil and compression/rebound only as far as I'm aware? Regardless: With all Argyles the spring assembly (the big you need for lowering) is on the left (as you would see it whilst sat on your bike) and the rebound and compression crap is in the right leg.
You take off the left top cap, unscrew the bolt at the bottom of that leg (giving it a knock with a mallet whilst it's still screwed into the leg to unseat it), pull out the rod from the top and slide the spacers onto it.
You take off the left top cap, unscrew the bolt at the bottom of that leg (giving it a knock with a mallet whilst it's still screwed into the leg to unseat it), pull out the rod from the top and slide the spacers onto it.