Thank F for that The vacuum idea succeeded in retrieving the bulb! I accessed the housing by removing the DRL bulb which enabled greater access.
I then had the task of fitting the LED sidelights and discovered that this time it went in easily and thus concluded that removing the DRL bulb whilst fitting the sidelight is the key to success. On the passenger side I proved this because the holder refused to go back in but once the DRL was out, in it went no problem
Just a note for anyone else planning on changing their sidelight with this method:
1: The sidelights only work one way around so try before putting it back in
2: When putting the DRL bulb back which simply twists and locks in place, you might find the wires from the sidelight are now in the way so you'll need to push those aside