I did a quick AI-assisted search. This hints at that the situation in GB is pretty similar as in Germany and the rest of West Europe (i.e. self-service is the norm).

Listed as countries where both exist (i.e. it is worth enabling this quest) are

1. Italy ("Almost every station has both Self (Fai da te) and Serviced (Servito) lanes")
2. Japan ("self-service was illegal until 1998, and the transition is still ongoing [...] You will see stations clearly marked as "Self" (セルフ - Serufu) and others that are Full Service") source.
3. Argentina (self-service was illegal until early 2025, transition ongoing) source
4. Mexico: non-self-service is the norm, but not outlawed source
5. Oregon, US: "As of late 2023, Oregon allows self-service statewide, but stations in "urban" counties are required by law to keep at least 50% of their pumps as full-service for people who don't want to do it themselves."

Would you please change the PR accordingly?

I'll do it myself.

For reference: 63c52ae