Finally on the right track though not there yet and a gin & tonic in the pool has my name on it.

The examples you get when you ask for an API key are out of date and totally different from the text in the 'Developer Archive' where the REST stuff has separate pages, and additional headers. All their docs are a bit broken, with responses from the site giving URLs that give a 404 when selected. A bit of a worry.

Anyway REST docs are at https://archive.clickatell.com/devel...-api-features/ though they have to be read in conjunction with oither chapters I think.