The HB is correct in claiming Ochta was the son of Hengest. This is supported by Bede. Although the ASC names Aesc as the son, if it is accepted that the 488 date is correct for Hengest’s obit then it would seem that Ochta was the name of Arthur’s opponent in some of the 12 battles.
As far as Esla of the Gewisse is concerned, as Sisam pointed out, Esla/Elesa formed an alliterative pair as did Wig/Giwis. Chronology would, therefore, suggest he was a contemporary of Arthur and identification with Osla Gyllellfawr is reasonable. The Culhwch ac Olwen, where we are told his dagger, Bronllafn Ferllydan, is used as a bridge and also that he was involved in the chase of the Twrch Trwyth, describes him as an ally of Arthur. However, in the Breuddwyd Rhonabwy he is an opponent at Badon, but asked Arthur for a truce. Perhaps, he defected to Arthur. If Esla was, indeed, an ally it may explain why DEB 26 states:
“tam desperati insulae excidii insperatique mentio auxilii”
“… ‘so desperate a destruction of the island’ – the Saxon revolt – ‘and unhoped-for mention of assistance’ …”
This unforseen help referred to may have been Saxons fighting with the Britons against Kentish forces. That may also explain the reason why the West Saxons claimed their dynasty started with Cerdic, rather than with the arrival of Giwis, possibly in 475. Although the ASC claims Cerdic’s obit in 534, Dumville dates it to 554. It is, therefore, likely that Cerdic was one of Arthur’s opponents at Camlan.
 Higham, N.J., 2018, 162.