The BBC3 site for Anna Lapwood's playlist says it's only available for a few more days, so I just wanted to put it here for future reference. It was so good.
Little note on kaitiaki, It's not a Mercer original, it's drawn very directly from Te Reo Māori. I'm from Aotearoa New Zealand, though I'm not Māori myself (just a Pākehā who does her best). Kaitiaki means more appropriately 'guardian' and the term it is associated with, kaitiakitanga, refers to the process of guardianship over nature and the environment in accordance with tikanga Māori.
While this is about the right sentiment for druids, it's sort of like greeting people at your local church with the word "priest." Like, if we accept that they're crudely using Te Reo Māori as a druidic thing (which, that's a whole can of appropriative worms along with the divorcing of the concept from tikanga Māori that I shan't open, they almost certainly chose the term when it was a home game), they are basically just greeting each other by saying "druid."
comment by Reddit user u/AdmiralPegasus