Many thanks to those who have responded to my post and addressed the points and questions I raised.
It's not the cost or the technical aspects that I'm concerned about personally. When I first went online at home nearly 25 years ago I don't suppose more than 20-30% of the UK's population was online then. People would ask me what the internet was, and in those days I helped a number to get online themselves, some of whom now have the latest bells and whistles smartphones. I've had a basic pay-as-you-go moble phone for nearly the same lenght of time as my internet connectivity but have never felt the need to access the web by other than my desktop - ten years ago I did switch from Microsoft to iMac.
My point really is why should everyone be expected to run their lives, at least in part, via the internet? I really do know people who would struggle with a smartphone if the only way they could travel was by using digital technology. If such things as vaccine certificates become a reality and can only be used digitally then I will have no option but to fall in line if I want to continue travelling abroad.
Once again, many thanks for the helpful comments. They are appreciated.