Please can you point me in the right direction to find out how to provide people with an unique URL that they can subscribe to which has a continuous sync so the calendars on their devices are constantly updated?
You can use the list view ics feed for this: http://glasllwch.org.uk/calendar/list/?ical=1&tribe_display=list. It will contain the amount of upcoming events you configured the calendar to show. If you want to make the feed include all year events (for example) I can provide a snippet to do so.
Yeap, that should be how it works. There might be some caveats depending on the software the user uses to subscribe to the feed. For example, Google Calendar might take up to 12 hours for changes to show (google calendar help center).
The best way to be sure of how this works is to actually subscribe to your own feed 😉
Please give it a try and let me know if you are happy with the result,
Best,
Nico