Have found a website (https://www.mylearning.org/ ) aimed at teachers and especially concentrating on the yorkshire area with some interesting stuff on it. Not much about birmingham, but does have a picture from the M&S archive of the inside of the Birmingham store in the 1930s. If I had just looked at it without a caption i would have thought it was Woolworths, but as it apparently comes from the M&S archive it must be M&S, though not as we know it now.