I have just subtituted the Maplins part no L57BA (5 metre DIN-to-DIN lead) for the old DIN-to-DIN lead. It works fine. I also tested the Maplins part no JB22Y (a male to male 5-pin DIN coupler) joining the two cables and that works fine too.

These tests were as the Slave lead between two rear speakers but I can't see any reason why the wouldn't work between Master speaker and processor (also a Slave lead situation) or for extending the Slave end of a Master lead.

In the spirit of Spinaltap, I would like to confirm that I am not involved in the corrupt theft of a global sport.