Luke is very good at quoting his sources. Yorkshireman John Davey's site dedicated to the history of Elmet. Check out the British Era and Dark Age Battles. Still heavily under construction at the moment though. Lots of Celtic personalities to be found here including Kings, Gods and Arthurian characters.
Most entries are extensive in detail.
Well worth a lengthy browse. Only up to H so far though. Original sources are extended here to cover the Historia Nova, Cyfraith Hywel, Gerald of Wales, Brut y Tywysogyon and Adam of Usk. Genealogies, often missed by others, from the Pillar of Eliseg, Bonedd Gwyr y Gogledd, Mostyn MS117 and soon Jesus College MS20. Also Welsh Christianity and Bibliographies.