Michael Chare wrote:

This makes me think that what I would like is a little box which would attach to
the radio CD connectors and then let me play music stored on a USB memory stick.
Any chance that someone will make such a product?


Limited market. The item would be custom to an CD Changer interface
standard chosen by the car audio manufacturer - these have a habit of
changing as time progresses.

Best to change your head unit to one with a USB (or SD) connector for
your memory modules. These are now available cheaply (from £50
ALDI/LIDL) and should hopefully be an easy swap-in for your VW's radio.

Funny, some time ago someone reckoned that the second market of user
installable car radio's would be dead by car manufacturers designing
dashboards to take their own customised equipment. I'm sure your VW
radio will come out ;-)

--
Adrian C