I found the trick to getting these parts to click together was to remove all switches/lamps etc, attach string to the loom connectors that you need and feed the string through the backing plate and then the corresponding hole in the cover plate. With the string in place your fingers will not be fighting for space against the loom coming through the hole and you do not need to worry about dropping the loom down the hole.
The two parts that click together seemed to do so only when they both lined up with each other and were perfectly centred in the centre console hole, it is one of the most frustrating pieces of trim but will go back together, when you have achieved this your fingers will look like S%*t.
With the two pieces back together pull on the string to draw up the loom connector, disconnect the string and pop it back in to the switch/lamp, press the switch and/or lamp back in to the hole.
Give the trim pieces a but if a wiggle to make sure they have clicked together before removing the string and pushing the switch/lamp back nothing more frustrating that when you get to the last part and it pops back off!!!!!!!