In New Zealand if you call the emergency number 111, the operator can automatically request the location of the device from the telco (with no opt out) if they belive there is a serious emergency and the location is not communicated. There is also some standardised way for the mobile phone to automatically send GPS coordinates to emergency numbers.

There's a standard for automatically sharing the current location with emergency services, which is supported by both Android and iOS [0]. According to the wiki article, the UK is even one of the countries that uses AML.

[0] https://en.wikipedia.org/wiki/Advanced_Mobile_Location

Bonus points: all modern browsers understand coordinate based location, no need to add an app.

AFAIK, this is required in the US. If you call 911 they can request your GPS position. All cell phones for that reason are required to do GPS. Even simple feature phones can do GPS in some way. They can acquire the GPS signal and then will forward that to the cell tower, which then is able to do the required calculations to translate that in coordinates. Somewhere around that line it was working, IRC.