From vital London, take the Piccadilly Line straight away 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 relevant London, take the Piccadilly Line rapidly to Heathrow Terminals 2&3, 4, or 5. Trains run usually and are funds-friendly.