Anyway, here's a few things I've learnt that might save other people a lot of time:-
- WebVR is already deprecated in favour of WebXR.
- There are very few browsers that actually implement WebXR. Firefox Reality is not one of them, despite the website saying "Firefox Reality was specifically designed to tackle all of the new opportunities (and challenges) that come with browsing in VR."
- In order to use the controller, your web page needs to be served in HTTPS, meaning you need to mess about with certificates.