I've made some amendments (copy from above) - sure enough the data we needed was inside the runtime property. BUT I found the solution!
The sodding datapoint query doesn't work in 3.7 without setting the script permissions.
Normally these were populated by default, but this is no longer the case. In this case, make the script permission run as superuser to get your points through, or at least the user allowed to read those points.
Once you've done that you'll be away!
Fox