A well packaged parcel arrived, thank you very much.
Cable: Works as expected.
DF0/DF1 switch: Not having much luck:
Switch position "A": Real floppy on internal connector acts as DF0. External Gotek not recognised (no 'click' on ejected disk either).
Switch position "B": Real floppy on internal connector acts as DF1. External Gotek recognised as DF2. There is an extra icon on the desktop DF0:NDOS.
User error? I had no idea how to orient the switch into the socket so used the time tested method of aligning the notch on the adapter to the notch on the CIA and then the socket. I have a A3000D, so U300.