Yep that's the one's Marky, grease the outer bush area making sure that lots of grease sits in those two deep grooves of the outer bush, that's what they are there for, to pool the grease.
Personally I would still persevere and get the collars out too even if it's a few mm, they will come out with persuasion on this type of arm... A light smear on the collar face is all they need. Belts and braces mate.
Yes, if you are intending on reversing the main bolt, the inner plastic wheel arch covers need to come out mate. Give the screws a quick blast of plusgas and using the biggest screwdriver you can find that will fit the screw heads give the end of the screwdriver a tap or two with a hammer then unscrew.. don't worry if they snap. Drill them out and buy slightly larger self tapper screws which will go in fine, no need to tap new threads mate... Halfords sell them in small packs. For added security use penny washers if needed.
Look at it this way, eventually those screw heads will rot away and the last thing you want is a huge lump of plastic flapping around and eventually wrapping around the brakes and inner wheel, so prevention is better than the cure
There is just enough room to get a 4" angle grinder cutting disc in once the wheel arch cover is out the way. Just remember to remove the ball joint and push the arm down as far as it will go but keep the nut on the end main arm bolt loose but knocked as far as it will go towards the spring. Cut through the bolt with the angle grinder as far as it will go then twist quarter turn using the nut end, cut again and another quarter turn, cut again until the bolt head is off completely. Use a file to clean off the swarf and using pliers or grips on the nut, pull the remains of the bolt back through towards the rear of the car...
Don't forget to remove the alarm box and evap canister from the engine bay brackets so the bolt can come all the way out and get the new bolt back in in reverse.
The rest is easy.
And..... When it comes to regreasing the bushes, you remove the covers again, loosen off and remove the bolt and simply twist the arm out towards you, no need to even disconnect the ball joint! A twenty minute job in the future