UPDATE: I've clicked on the provider dynamic parameter and now get this error when querying the Oracle DB.
Msg 7399, Level 16, State 1, Line 1
The OLE DB provider "OraOLEDB.Oracle" for linked server "xxxxxx" reported an error. Access denied.
Msg 7301, Level 16, State 2, Line 1
Cannot obtain the required interface ("IID_IDBCreateCommand") from OLE DB provider "OraOLEDB.Oracle" for linked server "xxxxxx".
Thanks