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.
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.