Will it be possible to take a train from Stratford directly into Heathrow?
The Stratford in London you can take the Central line to Holborn and then the Piccadilly line all the way to Heathrow. Or the Central line to Notting Hill where you can change onto the Circle Line to Paddington to catch the Heathrow Express.
If you mean Stratford UPON AVON no you can’t get a train straight to Heathrow.
You can take the train from Stratford upon Avon into London Marylebone.From there it’s one stop on the tube or a 10 min walk to Paddington for the Heathrow Express.
If you do mean the Shakespeare Stratford please don’t shorten the name, it does matter.