jbcollier, what do you believe could be causing what I would call excessive rear camber? I would judge it to be about 3.5 degrees. Would the cause be within the transaxle? Half shafts? Uprights?
The entire rear suspension is located by rubber (composite) bushings and mounts: engine, transaxle, trailing arms, shocks upper and lower, lower links. Deterioration of any (or all) of them could contribute to camber issues. The only 'fixed length' hard mounting are the axles through the u-joints through the outer stub axle, so, unless the u-joints are roached, I would take them out of the equation.
"Fixing" camber by only looking at the lower links does not solve the issue, only masks the misalignment or mis-location of other flexible mountings in the suspension system. And it is a system, not individual components that can be changed without having an effect on the other bits that make it up.
Start at the beginning. And that is:
1. Examine the bushings of ALL the components. From the big metalastic donut at the front of the trailing arm, through the engine mounts on the frame, to the inner and outer bushings on the lower links, the bushings on the shocks, to the rear transaxle mount to the frame. Are they deteriorating (crumbling, loose, oil soaked, etc?). Note which ones need replacing. Being this is an S1, I'm thinking that it would be false economy to just replace what's visibly shot..you're looking at, a minimum, 2 metalastics at the front, a set of 8 bushings for the lower links, and potentially both of the engine mounts and rear mount for the tranny. They can all be done in situ. Yes, it's that important. Start from known fresh and new.
2. Ensure the axles are shimmed and tight in the trans. Lift the rear of the car, put on stands (safety FIRST, LAST, and WHILE DOING) and check (with your hands at 12 and 6 o'clock on the tire) for play in the rear bearings. There should be NO movement back and forth of the wheel. Same at 3 and 9. If there is, you'll never get a repeatable camber reading; if the axles aren't shimmed, you run the risk of damaging the trans.
3. You DON'T need polyurethane bushings. You just don't, for normal road use. OEM style work just fine.
4. Check your shockers. If they're roached, you will NOT get either the ride height or location of the wheel where it needs to be. If they're not roached, then depending on the manufacturer, you can get them rebushed (or even rebuilt...I believe Konis are rebuildable) so you're starting from a known good point.
My reasoning is that the fellows in Hethel knew what they were doing when they drew this up and chose the items which would, within manufacturing tolerance, result in the car meeting its design specs. Like most things in the Europa (where a single part may be called upon to do multiple functions...the rear suspension is an ideal example), you have to look at parts in relation to the entire system under repair and sometimes (especially in the suspension systems which really make the car what it is...) your efforts have to go deeper than just the item in front of you.
Just my $.03 (with inflation). Good luck!