They are light years behind countries that have fully-fledged dynamic services provided by the government accessible through the ID Cards, as it is in the Baltics for example.
National ID cards are a particularly thorny issue politically, there's been a few attempts to introduce them, all of which have been noisily shut down in parliament because of privacy concerns. There isn't really any single database of people in the UK, with different ministries having their own databases. In principle this seems like a pretty good approach, even if it does mean that things like authentication with web services is a bit clunky.
https://gds.blog.gov.uk/2020/09/22/introducing-gov-uk-accoun...
I'd put forward Gov.uk/pay and Gov.uk/notify as very successful transactional services that operate on a massive scale. They have been particularly good for local councils who just hook up to Notify and Pay. The parts where security is paramount are handled centrally. It stops councils having to "roll their own".
Universal Credit is a transactional system handling billions in benefits. When the conservative government shut down the economy in March it seems to have coped pretty well:
https://dwpdigital.blog.gov.uk/2020/12/14/dwps-agile-respons...