Another vote for Windy. They now have the UKV High-res model (provided by The Met Office). The live rainfall radar is also Met data.
The other one to try is The Met Office official app. Depends what you’re after really. If it’s a general reliable forecast, official Met app. More layers, compare different models etc., then Windy.
Boost. There were several other great ones I tried, such as Sync and Relay, but Boost suited me best.