Someone that doesn't cover london/uk :(

Yup, sadly outside the United States, cost free weather data seems very rare. In my initial search I found many meteorology agencies (even those publicly funded) required payment or licensing for using the data.

For the UK, the service is Met Office and their licensing/pricing terms were enough to make me reconsider including that data in the first version.

I can supply you with the current conditions, daily forecast, hourly forecast, and severe alerts (US only) for nearly any city in the world for $0.02 per API call. I have access to more weather stations than any single source in the world. I can return the data to you using the conversion and format of your preference. If interested, you can find my email in my profile.

I use weather data from NOAA for this