I have already told you what causes me concern. In reference to your timeline above, the government are going to have to significantly improve their testing to meet a 2 day turnaround.
But more fundamentally, you have no idea if any of what you have written above is true until the code is released and independently verified. Does blindly trusting a government who has demonstrably lied and manipulated their way through this crisis not bother you?
On your laboured point around people who object to this but share with other organisations. To put it bluntly, it is becoming clearer and clearer in this thread that there will be a social stigma attached to choosing to not download the app. For that reason you can't compare it to someone willingly sharing their information. No one has questioned your choice to download it, the pressure is in one direction only. It is likely that those who decide not to download it but struggle to translate their concerns into words will be harangued and harassed into doing as they are supposed to.
I am surprised I need to explain this but the camera in the bathroom example wasn't meant to be an analogy but instead a demonstration of the fact that there is a spectrum of opinions and therefore personal decisions made around this app, your line will be different to mine. A really crazy person might even think a camera in the bathroom is appropriate.
I have tried to find as many independent experts in the field and take my lead from them, the overwhelming sense I get is that there are major and wide ranging concerns spanning multiple specialisms.
Found this enlightening from a ncsc/gchq perspective -
https://twitter.com/martinralbrecht/...794294784?s=20. You might think he is crazy to imply that we might wish to join those dots.
Interestingly, according to the FT, nhsx are already investigating into whether they could and should switch to the system being used by the majority of countries. One which appears to have the green light from a lot of the experts criticising our chosen approach.