Neil Williams wrote:

Quite. I for one believe that HEx - or at the very least the
stopping
service - should be subsidised and included in the Travelcard system,
just like, for example, express services to Manchester Airport are
within the GMPTE/National Rail fares structure.

It will be - services between Paddington and H&H on Heathrow Connect
will be fully valid using Travelcards. It is only the service between
H&H and Heathrow that will have a premium fare.