Fellow UK person - the style of exam that you describe is pretty hard to cheat unless you can find another person to go in your place. I think various institutions have tried digital invigilation but have had little success (and I think this is just a bad idea anyway).
However, you also mentioned a final project. You’d be shocked how much commissioning exists where people have their projects produced for them. I’m not talking an overly helpful study group, I mean straight up essay mills. Tools like ChatGPT make the bar for commissioning lower and cheaper. I don’t know how you can combat this and still have long-term projects like dissertations.
My final year project was a 120 page report of measurements of electron spin resonance together with the design of the experimental apparatus. I had to defend the design, conclusions (which I have long forgotten, it was in 1977), and justify the methods and calculation all orally to two academics.
I doubt that anyone could have produced a plausible report without actually doing the work. And to defend it one would have to understand the underlying physics and the work that was done. Plus I think my supervisor and the other two students who worked with me on the project would have remarked on my absence from the laboratory if I had simply bought the paper!
You can still have long term projects and dissertations so long as the degree is awarded for the defence of the dissertation rather than the dissertation itself; that is the student must demonstrate in a viva that they understand everything in the dissertation rather than merely regurgitate it.
I think that in your case you've correctly observed that it would be nearly impossible to commission or otherwise fake your particular dissertation/project because of its experimental nature, and that you were called to a viva.
There are certainly similar projects being completed by students every year, and doubtless those students are not cheaters, but for each dissertation like yours, there are probably 10 or more projects that are not collaborative and have no artefacts or supporting evidence other than a written report. Such projects are fairly easy to commission. For a reasonable price (potentially thousands of dollars) you can pay a poor research student in the same field as you to churn out a mid-tier dissertation. This can be detected with a viva, but the academics need to be very confident before accusing someone of cheating. More often than not, you can get away with it and just get a not great grade.
I think that in general the natural/formal sciences don't suffer nearly as much as social science and humanities do, simply because exams and labs tend to highlight irregularities, and cheaters are less likely to be drawn into "hard" fields. However, it still exists in every field.
That won't work in a tutorial system, the student will be quickly discovered to know nothing about the subject. And in open note finals, as in the Exeter Uni. Physics department of the 1970s, regurgitation of course material was of very limited utility because you were never asked for that kind of response. The quantum mechanics final didn't ask a single question that had been directly answered during lectures, it asked us to extend what we had learnt. That exam was what I think Americans might call a 'white knuckle ride'. Open note finals really sort those who understood the subject from those who thought they could just look up the answers, the invigilators spent a lot of time shushing people searching through rucksacks full of notes.
Many years later I took a course in C# at a university in Norway and that was not merely open note but also open book (you could take the set book in). Again that gives the exam author the possibility to really discover who knows what.
I doubt that your rich middle-western student would have passed either of these
However, you also mentioned a final project. You’d be shocked how much commissioning exists where people have their projects produced for them. I’m not talking an overly helpful study group, I mean straight up essay mills. Tools like ChatGPT make the bar for commissioning lower and cheaper. I don’t know how you can combat this and still have long-term projects like dissertations.