I got this reply from freedompass.org but I still don’t feel confident!
Thank you for your email.
I can confirm that you can use your pass on the tube to Heathrow at any time. I have also attached a link to our travel map, on this you can see Heathrow on the far left with a blue line linked to it, indicating this.
You can now also use the disabled Freedom Pass on TFL rail services between Paddington and Heathrow (those that were previously Heathrow Connect ie the 'slow' trains to Heathrow, not the Heathrow Express):
Replies
Thank you for your email.
I can confirm that you can use your pass on the tube to Heathrow at any time. I have also attached a link to our travel map, on this you can see Heathrow on the far left with a blue line linked to it, indicating this.
https://www.londoncouncils.gov.uk/services/freedom-pass/using-pass/freedom-pass-travel-map
I hope this information is of use to you.
Kind regards,
https://www.londoncouncils.gov.uk/node/36801
It is the orange dotted line on the above map going north from Heathrow to Hayes & Harlington.
That is as well as the Piccadilly Line and all London buses to Heathrow
Liam