Most visitors arrive through London, which has two major international airports. Heathrow (LHR) is the main hub, handling flights from across the world and connected to central London by the Tube and the Heathrow Express. Gatwick (LGW) and Stansted (STN) handle budget carriers and have train links into the city. From mainland Europe, the Eurostar from Paris or Brussels to London St Pancras takes around two hours.
By Air
London Heathrow is the busiest entry point, served by most major airlines. Budget carriers — Ryanair, easyJet — typically use Stansted, Luton, or Gatwick. Booking ahead gets dramatically cheaper fares, and flying between English cities is rarely worth it given the short distances.
By Train from Europe
Eurostar runs high-speed trains from Paris Gare du Nord and Brussels Midi to London St Pancras in roughly 2h15 and 2h respectively. It's a civilised way to arrive — you clear customs before boarding and step out in central London.