Hi @tom,
Thanks, I managed to get the access token through using the client_id and client_secret in the body with the No Auth option) and that all is working.
I would like to get it working using a username and password if possible. My plan is to have a very fine grain access control based on the user logged in so I need to be able to use those details instead of the client id and secret if possible.
When using Basic Auth and entering the username and password I get the first error that I mention above ( invalid_client ). Is it possible to get an access token based on an individual user? And if so do you know what requests I need to use for that?