@paulsmith I have to admit I'm not that deep into the Delphi code here. My responsibility ends where data is received. 
but I've seen the Devs use TRESTResponseDatasetAdapter and feed it with the JSON response.
Unfortunately I cant share enough of our code that would help you but I did a quick google and maybe these examples will help you get it running:
- https://appmethod.wordpress.com/2014/08/10/restjson-and-a-listview/
- http://blog.marcocantu.com/blog/source_code_mobile_music_client.html
On the other hand, you dont have to use TRESTResponseDatasetAdapter at all. You could also read and use the JSON response yourself.
(Personally, I'm not a big fan of all those "magic" Delphi components anyways. I've seen them failing or behaving in a weird unpredictable way often enough. And they are terrible to debug 
)