London – Heathrow Express is warning customers that there will be no service on August 23, because of Crossrail improvement works being carried out by Network Rail. A revised Heathrow Connect stopping service will be operating between London Paddington and Hayes & Harlington only. Passengers wishing to travel between Hayes & Harlington and Heathrow may use the 140 bus service free of charge.
https://www.heathrowexpress.com/timetable-schedule/service-plans