[Just seen this - I don't often visit the GPS board!]
You might be better asking in the Audax board. But the route is very likely to be the same as the "Brevet Cymru" from previous years. Google will find you some routes; e.g. I found this from the 2015 ride:
*CHECK THIS AGAINST THE ROUTESHEET BEFORE YOU USE IT*https://www.strava.com/activities/297623043*YOU HAVE BEEN WARNED!!!*
Also; you might find that in the week leading upto the event, there is a lot more chatter, and someone else might make a gpx/tcx that you can steal.
It's a great ride - I rode some of the route last weekend on my way home from the club trip.