Forecasting the weather is not easy, which is why forcasts often differ. And then there are local variations - in time and region - something that no forecaster can address.
Most people have thier own sources, radio, television, newspaper, website etc and for the latter there are the following below, centered on Kenley in South London (which may imply accuracy but is really over a larger area):
Needless to say these should be regarded only as a guide, and the suggestion of these websites rather than any other does not reflect any bias of the society; they are likely to be no better or worse than others.
For those websites that require a location the postcode for the observatory at Kenley is CR8 5EP