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It's not exactly procumbent either.
Stace says that in O. corniculata, the pedicels are patent or reflexed in fruit, while in O. stricta they are upright. I think the photo fits the former description better. This is a weed in part of my garden but I'm not familiar with the upright species.
about the pedicels, and there is also the point about umbellate versus cymose inflorescences.
I've had another look at the plant, and taken a couple of more photographs. It is not rooting at nodes, and this is not just because it's growing over rocks. I tried keying it out in Poland and ended up with Oxalis dillenii (which is intermediate between Oxalis corniculata and Oxalis stricta).
I also have Oxalis corniculata as a weed, and this looks different. But further reading tells me that Oxalis corniculata is variable, beyond the distinction between the green and purple-leaved forms.
Please post pictures of the other plant you think is Oxalis corniculata.
You need a hand lens to see the white patchs on Oxalis dillenii.
BTW: The rooting at the nodes character is rather variable, but both O. strica and dillenii are much more erect that the plants in your photos!
I do agree that your plant looks different to the usual form. It looks quite purplish in the photos, O. dillenii only has green leaves - not sure how significant the purple flush is. The only other clue is that apparently the seeds have white patches in O. dillenii - how good is your eyesight?!
Lat/Lng: 53.1297484, -2.1621455
OS grid ref: SJ892591