ok got it working now...
I put the device templates back to their original settings ( including templates 1920, 1811, 1181, 1141, 1754 )
Looking through my original log as listed in this topic http://forum.linuxmce.org/index.php?topic=11227.0
, i can see that the script 99_PLCBUS_1141.sh is being called.
From looking at device template 1920 as suggested by TKMedia, i now know that it is that device template that tries to kick that script off. As such, to get things working all i had to do was change the 067b2303 value in the plug n play data in this template.
Previously i had changed the plug n play data in all
the above listed templates including 1811, whereas i should only have changed it in 1920 as evidently it was this one causing the conflict.
i think the important point in my case here is that i should not have changed anything on 1811, if i had only changed 1920 and 1754, TKMedias suggestions would have worked...but i tinkered a little after the original change to 1754 did not resolve the issue including making the change to 1811.
But all good now
TKMedia, thanks very much for your help!