Resolved but not happy
from the command line I have to use the /conf[iguration] switch to specify the location of the config file which will then override the location specified in the dtsx. I can understand why you would want that functionality in the DTEXEC armoury, but it shouldn't be the default method - you would have to specify it for every config file for every package - makes it a right PITA for support!
Which is probably why most people use an SSISConfig db to contain all config settings & indirect XML config to point to the SSISConfig db to use (dev/QA/Prod etc).
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