IME those apps often have the HTML/JS embedded, so you would have to extract the contents, host them somewhere and proxy the API calls.

I dunno, I haven't reverse engineered it to find the URL. But I would imagine it gets confused about authentication.

Would put money it on it using something like '?device_verified=1'.

You go to the nhs webpage and it works in the same way.

Login is better on the iOS app as you can use touch id/faceId and not userid/password also the webpage asks for cookies as it can't seem to remember the choice

Really? What's the URL that would allow me to see test results and book appointments?

Unfortunately that seems to depend on who did the test or your GP.

There seem to be sites for your GP (which mine does via a .nhs.uk domain it used to be via https://account.patientaccess.com/ which still shows appointments but does not allow booking but still allows requests for repeat prescriptions.) or hospital portal for results.