Both Heathrow and Gatwick airports are well-connected to London's extensive train network. The Heathrow Express is a high-speed train service that connects Heathrow Airport to London Paddington Station, from where you can easily catch a train to Gatwick. Similarly, Gatwick Airport has its own dedicated train station with direct services to London Victoria. While train services offer a cost-effective option, they may involve multiple transfers and require navigating through busy train stations with luggage.