The PCB arrived 10 days ago but I had not written yet because I did not have a chance to do the soldering job (and thus test it) until now.
At first, after transferring the flash chip from the old to the new board, it still didn’t work. I was quite disappointed! Then I noticed that two of the contact pads on the underside of the board were missing (?) so I remade them, by soldering a thin wire through the PCB hole and over each pad, and it then suddenly all worked.
Thanks a lot! Your help in sourcing a matching part, and your advice both on the web site and by email, has been invaluable and I am very grateful.