Having done this job today thought I would do a how too guide incase anyone else wants to take on the job.

Did this as the lower ball joint failed the MOT, this is built into the arm so replaced the whole unit.

Tools needed:

Socket set (8mm, 10mm, 16mm, 17mm, 18mm all used)
Screwdriver set (pozi and Torx bits used - T30 torx I believe)
Spanner set (only 17mm used)
Breaker bar
Decent sized Hammer
Ball joint splitter
Jack & Axle stands

May also want penetrating spray, Copper slip or similar and torque wrench.

First of all crack off wheel nuts as the wheel will need to be removed, then jack the car up and place axle stands underneath (I put mine on the main subframe but may be better elsewhere)

Removed wheel then removed front bumper (this I believe is elsewhere but there are three pozi screws each side, two just inside the arch and one underneath, torx screw inside the arch attached to inner wing, three torx screws underneath and four torx screws under bonnet, then take care to pop bumper away from wings and remove light & horn connectors.)

Once bumper is removed, you can get to the front crash structure, This is the bracket at the bottom with four 17mm bolts, top two and maybe bottom right can be undone with socket and rachet but bottom right needs a spanner due to intercooler pipe being in the way on standard setup.
IMG_6093 below

Once these four are removed there are three bolts holding it onto the front subframe, Two below and one on the side, two below are 18mm bolts which may need a breaker bar and then a 16mm bolt on the side. Once these are removed the crash structure is able to be moved.
IMG_6095 below

To remove the crash structure fully the intercooler will need to be moved and the washer bottle freed to be lifted slightly, the intercooler is moved by removing the duct to it with a 8mm screw, then a 10mm bolt on the radiator bracket. then washer bottle is two 10mm bolts each side of the bottle.
IMG_6108 & IMG 6109 below.

once these have been moved the crash structure should be able to be wiggled out, which will give access to the front bolt of the suspension arm.
IMG_6097 below

Now that you have access to all three bolts holding the suspension arm then crack all three bolts off, front bolt and rear bolt are both 18mm bolts and the Ball joint bolt is a 17mm bolt with a 17mm nut. Once all are cracked, Remove the ball joint bolt, mine was a pain due to a huge amount of rubbish on the bolt that meant virtually all the threads were no longer visible. once out knock the ball joint out, I did it using a ball joint splitter, then the two 18mm bolts can be removed and the suspension arm should be able to wiggle free (maybe use some penetrating spray to help lubricate the bushings to easily remove the arm).
IMG_6029, IMG_6030 & IMG_6098 below.

Then get the new arm and fit back in the reverse order, again a little spray to help slide the new arm in, fit the two 18mm bolts but don't fully tighten up Tap the ball joint into the hole and fit the 17mm bolt in, then all three bolts can be fully tightened up.
IMG_6102 below

The 'crash structure' can then be fitted back into position, Fit the side 16mm bolt first and tighten but not fully tighten, just so the 18mm bolt holes line up, then bolt in the two 18mm bolts, again don't fully tighten so there is movement to line up the four bolts at the front of the structure.
IMG_6103 below

Then line up the structure with the front bolts and bolt these 17mm bolts tight to hold it into position, when all four of the front bolts are tight then the three that attach to the front subframe can then be fully tightened.

Once these are fully tightened check all the bolts are tight, then the front bumper can be re-fitted in reverse fashion and the wheel put on.

This should then be the front arm changed.

Thanks 

looked for pointers a couple of weeks ago when I found out it needed changing and found nothing, so just had a quick look underneath and worked out when needed doing so thought I'd sort out a how to for others who are unsure whether to take the job on or not.

It took me 6 hours but I did stop for pictures, have bent lower strut brace to sort out and then cleaned and coated all the bolts I removed to make it slightly easier in future. I would give 4 hours to do the job again and nearside looks like it would be slightly easier as there is less in the way of the crash structure.

Have to say it isn't often I feel a sense of achievement when I've done something on a car but this was definitely one of them!

hoping to do more in the future If/when jobs need doing

Paul

Wow 10k miles and it needed to be replaced?!