Overnight travelers can use Night Tube services on the Piccadilly line on weekends

https://andersonmfey903.theglensecret.com/getting-to-heathrow-from-luton-best-value-routes-door-to-door-1

Overnight travelers can use Night Tube services on the Piccadilly line on weekends, or consider night buses that connect to Heathrow’s central bus station.