score:5
At a convenient location along the route change from the 285 bus to the 490 bus. These buses share a route for several miles, so there are countless places you can change between them, with the last being Hatton Cross Station.
The 490 goes to Terminal 5, but not before it stops in Terminal 4.
Depending on exactly which bus you end up catching, this will get you to terminal 4 potentially in even less time that it would have taken to get to the Heathrow Bus Station.
Upvote:2
You can do this by taking the N9 bus to Heathrow Terminal 5 and then taking the 482/490 bus. This will take around 20-30 minutes depending on bus times and take you directly to Terminal 4.
The buses run quite regularly, around every 10 minutes. TFL buses in the Heathrow area are also free.