Going to that website has obviously jogged some memories from when I last did anything with JP1 and I went scouring my hard disc.

I found a file from when I was trying to setup my Squeezebox using Pronto codes and this mentioned JVC DVD codes. As an experiment I reconfigured the MP3 button as a DVD on the remote and then went through the simpleset process for JVC DVD players and low and behold the squeezebox turned off. Problem solved!

Though I should add the code in case anyone else was looking. JVC DVD code 0623