I'm really surprised @hvert that proof is by card only. Over here we have an NHS app which you have to register for with your patient ID, apparently you can download/print off too but I've never done that. I'm sure it would be fairly easy to forge/screenshot however.

There is an irony here, we have the technology in place but no where I know of is asking for proof of vaccination except for border entry. No venues are requiring it. Yet I am reading you don't yet have technology in place but venues are asking for proof?

I honestly don't see proof of vaccination ever being accepted practice in the UK, it's something in the British psychology, a personal liberty thing possibly. There would be a backlash I suspect if places introduced it.