"My data source has a mix of individuals with a first and surname and others with an organisation name. How do I bring them in ensuring that the individuals and organisations are set up correctly?"
When you create a constituent mapping select the combined type as shown below:
Map the organisation name (in this case the Company column of my file) to the key indicator field. Then select the key indicator mapping's field settings:
Set up the data transformation as below:
This says that when the field is blank i.e. there is no company name then it should be an individual. Otherwise (using the catch all functionality) it should be an organisation.
We do a similar thing with the organisation name and with the last name.