Welcome to the forums AussieSeven! Looking forward to hearing more about your car.
My car has never had correct carpets, and as you can see by the side rails, what was in it, was disgusting/embarrassing. The GAHH kit, while "not correct" either in color or material (Wilton Wool, not velour) looks really good. While I'm excited to see the car look more presentable, I'm not very happy with the quality of their kit: I specifically asked to have a side pad in vinyl, next to the accelerator pedal. I was told by the sales rep, that she'd take care of it. She didn't. So that's a phone call for tomorrow. The piping is a replica of the Congnac leather, and while it looks nice, I would have preferred a solid color, which may have originally matched the brown color of the long rubber mats at the door thresholds. They didn't mention piping color choices, so there I was assuming that with their reputation and all their listings for specific W111 models, they were working hard to make their kits as OEM correct as currently possible. The piece for the center console is cut too large by about 1/4", so once set down into the console, the piping catches, and puckers the carpet upward, creating a low bubble shape. That's pretty frustrating. Basically they cut the carpet to the precise dimension of the console, and didn't account for the piping making it wider. Novice mistake, and for $1400+ I simply expect better. Again, it's another topic for a call tomorrow. The floor mats fit similarly. Literally so tight that they have to be forced down, almost won't just set flat because they want to buckle. The tunnel piece doesn't travel toward the firewall far enough to make it more forward then the floor mats, so that it's side edges are hidden by the mats, so there's a slight air gap there. Again, c'mon...how many of these have they done, to not have this really dialed in. It's going to be interesting to see how the side rails and rear tunnel fit. The pieces under the rear seat aren't visible, so I don't really care about them.
As far as how they mount, no, there are no snaps, or metal rings to fit over studs in the floor. That said, as I mentioned, the floor mats fit so tight, I doubt they will ever move. They come with what appears to be a closed cell, gray, foam, glued to the backs of the 4 floor mats.
Overall, I'm very happy to see the car look better, however, it's more like a $500 kit, or one of the kits that pops up on ebay, and not like a kit that was sort of "custom made from patterns and questions about whether the car had A/C, and did it have a floor shifter." I didn't ask for the order to be rushed, and that appears to be what happened. Frustrating, because I wasn't looking for "wham-bam, crank it out." Nor was I wanting to pay cheap, and wind up with cheap results. You'd think that if a company is selling restoration carpet for a high end car brand (Mercedes Benz), they would acknowledge that the customer is doing significant restoration work, on an expensive vintage car.
A note about the Putt Geogie Ltd carpet. I was not able to get it to photograph, but it shined as if I'd just wiped it with cooking oil or baby oil, and became very pink looking.