In this case you can try to check when is the earliest Heathrow express departuring from Paddington. It takes 15 min if everything is running fine. I heard that London is planning to run 24h underground, check more updates-- this could be helpful as well.
I heard that London is planning to run 24h underground, check more updates-- this could be helpful as well.
https://www.heathrowexpress.com/timetable-schedule/london-heathrow