Take the Piccadilly line from central London straight to Heathrow; it’s affordable, frequent, and stops at all terminals

https://cesarksrk986.theglensecret.com/heathrow-airport-map-for-arrivals-and-departures-access-and-transport-1

Take the Piccadilly line from central London straight to Heathrow; it’s affordable, frequent, and stops at all terminals, though it can be crowded during peak travel times.