A direct case was not reported in the UK in recent years, but evidence of very likely polio transmission was found in sewage samples two years ago:
https://nationalpost.com/news/world/polio-virus-found-in-uk-sewage-samples-risk-to-public-low
A similar situation happened in New York where an actual case was found a month later:
The short of it is, when vaccination rates fall, Polio can be reintroduced via transmission of the live virus found in the oral vaccine, usually taken in poorer countries. If someone were to take the oral vaccine and then immediately travel to a country with lessening vaccination rates, like is currently happening in the west due to the spread of right-wing conspiracy mongering, the live virus still in the vaccinated individual has a low but not zero chance of propagating to the unvaccinated or immune-compromised population there. Samples containing these vaccine-derived viruses are found a few times per year in most places, and it’s a weaker virus so often it leads to no symptoms, but in very rare instances it does take hold with the expected effect:
https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON366
Despite individual cases of polio turning up, either via direct reporting or evidence found elsewhere, it would still be correct to describe polio as being “eradicated” in these countries, at least currently. Nobody is confused by this or demands reclassification of the status of polio.
Something you might want to look into is using mTLS, or client certificate authentication, on any external facing services that aren’t intended for anybody but yourself or close friends/family. Basically, it means nobody can even connect to your server without having a certificate that was pre-generated by you. On the server end, you just create the certificate, and on the client end, you install it to the device and select it when asked.
The viability of this depends on what applications you use, as support for it must be implemented by its developers. For anything only accessed via web browser, it’s perfect. All web browsers (except Firefox on mobile…) can handle mTLS certs. Lots of Android apps also support it. I use it for Nextcloud on Android (so Files, Tasks, Notes, Photos, RSS, and DAVx5 apps all work) and support works across the board there. It also works for Home Assistant and Gotify apps. It looks like Immich does indeed support it too. In my configuration, I only require it on external connections by having 443 on the router be forwarded to 444 on the server, so I can apply different settings easily without having to do any filtering.
As far as security and privacy goes, mTLS is virtually impenetrable so long as you protect the certificate and configure the proxy correctly, and similar in concept to using Wireguard. Nearly everything I publicly expose is protected via mTLS, with very rare exceptions like Navidrome due to lack of support in subsonic clients, and a couple other things that I actually want to be universally reachable.