[update]
I have used the experience endpoint as a workaround for my problem with the length of the webhook URL (thanks to Webhook too long for server).
The data is coming in nicely in data instead of query, without changing the content-type:
Do I need to create an Endpoint reply node in my workflow? With or without it I get this response:
{ "error": "No endpoint found for this route" }
Cheers
Jules