You can use Ofcom's coverage checker to check indoor and outdoor mobile coverage for telephone, 3G, 4G, and even 5G services from all major providers. Simply enter your postcode or let the checker automatically find your location. The checker provides an overview of services in your area and an interactive map to view coverage. It's important to note that coverage predictions are generated using computer programs and may not always reflect actual on-the-ground coverage. Therefore, it's helpful to also speak with people in your area about their experiences with mobile coverage.