Had a go at this yesterday to replace indicator bulbs to LED. Thanks for the mega helpful guide! Although there are a few folk who have managed this without taking the wheel liner off, I would say don't even try it - those 2 bolts tucked in behind the wing are almost impossible to remove otherwise. I tried with a bendy screwdriver and just about managed on one side, but was starting to rip the torx screw head, so spent 15mins getting the wheel off and then wheel liner, and am so glad I did! At the bottom of the wheel liner at the front end there is an attachment that looks like it is clipped in - this pulls out rather than down, so you are pulling it towards the wheel rather than down to the ground.
Also a little tip for when you're putting everything back together... loosen the top torx bolt on the headlight (there are 3, the other 2 of which are lower down on the unit - one at the back and one at the side), which will drop the headlight unit by a few millimetres, but made life easier when putting the bumper back on, as there are a few slots on the base of the headlight unit that align with holes in the bumper, and this makes it easier for those to connect.