Thanks for the reply.
As part of a production line refresh we are installing on 180 clients and would just like a silent installation with headers to a non default location but can't find any information on how to do this using command line.
So is this not possible ?
Not possible by design. Any given machine can have many OPC applications installing the core components. If the installer allowed any of them to change the default locations they would break other applications.
I realize that there are cases where vendors are sure that they are the only one installing core components, however, these are the exception and the installer has no way to automatically detect if this claim is actually true.