Hi Pete. I too am most comfortable with all things south of the river. However, one of the many railway books on my shelves is 'Railways in and around London Then and Now' by John Glover. In that there is a photo of Silvertown station in March 1977 with a concrete footbridge, Grays in November 1980 and Pitsea in May 1980. They all look very much like the Southern ones to my untutored eye.
Cheers,
Terry