Peter Crosland wrote:
Once again, I am reduced to handing around the nursery stable
yard.........

I am after a 10 M A - B USB cable (with repeater).
snip
There must be other ways of doing what you want such as serial port to USB
convertor.

Once the cable is in, you've got very good flexibility.
It can be used to attach a webcam, printer, scanner, lava-lamp, ...

Serial is inherently pretty limited.