Hi Mat,
Did you have luck meanwhile, or are you still stuck. I assume you have already added a debug node to the output of your http-request node? Does that give any clue?
I have just released version 2.0.1 of the node-red-contrib-http-logger, since the previous version didn't support recent NodeJs versions. Don't know if that could somehow be of any help for your troubleshooting? But (at least if my new version works correctly) then you could compare the request send by the http-request node, and the request send by the browser (via your browser's developer tools) when you specify the url directly.
