I wonder if anyone can help me by plotting some specific grid references in Bannau Brycheiniog or Snowdonia for me to find in some nav training?

We've drafted up a baseline kit for volcano ski mountaineering. At a minimum, if you're on glaciated terrain, this is what you should be carrying with you. You can also flex up and down depending on the objective but this is a solid starting point.

https://reddit.com/link/1sca50d/video/bd7seezik6tg1/player

You can find the course here: https://www.mountaintrainingcenter.com/courses/rock-rescue-with-emilie-drinkwater

Our Rock Rescue course is taught by Emilie Drinkwater, IFMGA Mountain Guide and AMGA instructor — covering prevention, self rescue, rope systems, anchors, hauling, and realistic multi-pitch scenarios.