Think you need to include a valid referer in the html header.
Just tried their ajax check method using a soap/rest client and seems to work here.
If you go to
https://api.superfastmaps.co.uk/openreach/1.2/ however you will notice that the response is a html comment stating:
<!-- There was an error trying to load the page. -->
<!-- Non-referer traffic is not permitted. Please try again on another computer/device. -->
Edited by cymru123 (Mon 12-Dec-16 22:09:18)