From critical London, take the Piccadilly Line instantly to Heathrow Terminals 2&3, 4, or five

https://www.scribd.com/document/1074929924/National-Rail-to-Heathrow-Routes-Transfers-and-Tickets-Explained-232993

From principal London, take the Piccadilly Line directly to Heathrow Terminals 2&three, 4, or five. Trains run mainly and are budget-pleasant.