Here you'd probably want to use local automatic weather stations (AWS), which are a superset that includes major airports. There are lot more of those around London than just Heathrow. I imagine NOAA has a similar setup.

https://www.metoffice.gov.uk/research/climate/maps-and-data/...

I'm not sure if the CAA and Met Office share stations though. Airports often have more specific instruments like ceilometers to give measurements of cloud layer height, while AWS might have more cliamtologic things like pyranometers for sunlight hours.

I live in the US and use my local weatherstation to control my basement dehumidifier and decide whether or not to turn the thermostats. The airport is about 10miles away but actually doesn't have all of the data that I need, such as soil temp, leaf moisture, and it's not very local to my specific house which has lots of trees and tends to deviate from the airport that is more exposed. I still use the airport data, but integrated with my own local data to get a better picture of what's going on.