For the UK, the MetOffice is the official source of weather information for aviation and it would be good to familiarise yourself with coded TAFs and METARs as well as lapforms 214/215 for significant weather and spot winds that you'll use for flight planning. Windy, Skyvector etc. are great for the big picture as well as good for 'real-time' forecasting (i.e. you can see where the rain has passed). If training in the UK, MetOffice weather is what you should expect to find on the walls of the planning facility.