CN, when I last worked at Perivale there was an almighty footbridge across said chasm!
Staying on the positive, I also remembered the 95 Bus stops right by the footbridge, you can get the 95 from Shepherds Bush (Netwwork Rail, London Overground and Central Line), Wood Lane (Hammersmith & City and Circle Lines), White City (Central Line), Park Royal (Piccadilly Line)and Hangar Lane (Central Line).