Just an extra piece on Gwallawg's battles also possibly matching the battles of Arthur.
I wish to give a possible example of wholesale all 9 battles as a set recycling/lifting rather than single battles recycling/lifting. In the case of the Pa Gur the 9 battles sites are apparently the same sites/battles (as ones of Nennius/HB), but in the case of Taliesin's battles of Gwallawg (Song on Lleenawg) they are apparently different sites (though corresponding to the HB/Nennius/Arthur ones). Yet there does seem a parallel between Gwallawg's and "Arthur's" (Aurelius'/Ambrosius'?). Gwallawg was either copying or was semi-artifically compared/corresponded to the 9 battles of Arthur/Ambrosius.
If they weren't definitely different persons/times/places i would have thought Arthur was Gwallawg. Taliesin's Gwallawg battles piece possibly seems to imply that Maelgwn fought the last 1/2/3 of the HB battles?
There are a few numbering uncertainties of the battles. (I may be wrong separating "Aeron and Arddunnion", and i may be wrong uniting Beit and Mabon? Mabon i was not sure of the match, but being a hunter may be Celidon? May also relate as a "divine youth" to Merlin Wylt/Sylvestris/Caledonis? Though not sure if Taliesin means different battle (site) to Beit?)
If we only number by ones actually stated to be a battle then Agathes and Bretrewyn as 1st and 2nd would corrsepond to Glein/Tritbuit 1 and Dubglas/Eidyn 1. Bretrewyn's meaning may not match Dubglas / Othona/Bradwell/Maldon though? There is a Lleenawg before them which sounds/looks abit like Glein, but it isn't said/implied to be a battle, though it is a "defence" so may be.
Some orthodox scholars have suggested that Breguoin of Nennius/Arthur is lifted from Bretrewyn of Taliesin/Gwallawg. Agathes & Bretrewyn may be similar to Bregion/Breguoin & Agned/Castle of Maidens, but they are in a different place/order (which i am not sure if is so, and if so then why so). Not sure if Taliesin allows for Agathes & Bretrewyn to be same battle site though? (They may be different battles at same site, first one was a defence, which would parallel earlier Anderida/Pevensey massacre and later Bregion/Agned battle?) If they are the same then we see that the lifting/recycling was the other way around, because Gwallawg is after "Arthur"; and we see that the 9 battles are a genuine set of 9, not composite, because not just lifted one/few but correspondence of all 9; and we see that the HB one is not same actual battle/site as the Gwallawg one, only parallel.
Our tentative numbering re matching with the number 9 of HB/PG are: 1 Lleenawg, 2 Eiddyn, [8a Agathes, 8b Bretrewyn,] 3 Aeron, 4 Arddunion, 5a Beit, 5b Mabon, 6 Gwensteri, 7 Terra, 9 Oleddyfein.