I went for the westfalia detachable tow bar on my 2012 R Design. Fitting was as described before in a few of the very helpful posts.
I removed the silver trim from the bumper as gave better access for fitting the towbar, although a nightmare to get the two sides clipped back in to replace the trim.
I ordered the wiring kit (13 pin) from Volvo Aberdeen who were very helpful, trailer module and installation kit for the R design. Wiring kit was the easiest I have ever fitted (Fitted a Corsa, Toyota Verso, Insignia and also a Kuga).
I have found out that the installation kit (£46.99) is only for the original thule towbar. Not any use for any other towbar. (it is two exhaust brackets and fixings to lower the two exhausts. So if anybody is looking for a cheap kit for a thule exhaust, give me a shout.
I can confirm that the right hand side exhaust is about 20mm clear for the towbar and no spacers needed. The left hand side was a lot closer, so I fitted the two 10mm spacers and M12x50mm bolts that was supplied with the westfalia towbar, which dropped the exhaust bracket down a bit (but not noticably lower than the other exhaust).
The front two bolts are the easiest to fit. We used a trolley jack to ease the towbar up into position to put the other two bolts into each side. Just remember to put the back bolts into the bracket before placing into position (as they wont fit once bracket is inside, one mistake I realised quite quickly. LOL).
Overall fitting took about 3 hours with two persons a real necessity..
The software upgrade is to switch off the fog light when caravan/trailer fitted. Volvo quoted £16.99, but that didnt include workshop charge. Don't think I will bother