BBC's weather (which will cover the world) is in my experience not greatly accurate (i.e. correct). You could also try www.uk.weather.com and www.accuweather.com. But in the end it is only a forecast so in Europe one should expect the actual weather to be slightly different, especially in the UK. Be ready to see the forecast vary with time, as if they can't quite make up their minds which horse to back. As a matter of interest, for my UK location I watched all three closely for today because I was doing something highly weather (no rain) dependent. All three were different but uk.weather.com was closest to correctly predicting what actually happened.