Thanks, effectively this site seems to be requiring the same parameters as a web browser submit form, rather than the more normal content used by REST APIs.
The ICS TRestParam class can already generate seven different content types, Json, UrlEnc, XML, CSV etc, so I need to add FormData as an eighth content type, I'll look at it next week.
Effectively this will be a more generalised version of the file uploading code I already recommended, but without actually uploading a file which it seems was a red herring.
Angus