WI: Complete victory for Aethelstan at the battle of Brunaburh

[The Anglo-Dutch Union]

So the battle of Brunaburh was between the newly created kingdom of England and a coalition of Britons, Nors-Gaels and the kingdom of Scotland. The battle was a result of of Aethelstan's campaigning in the north, and the coalition attempted to halt the expansion of England by invading it. This invasion resulted in the battle of Brunaburh which was a pyrrhic defeat for Aethelstan, for altough he was victorious and england was still united his campaigns to the north were halted and after his death Northumbria temporarily became independent. So, what if the battle of Brunaburh turned into a total victory of the english? Could they have conquered the entirety of the bristish isle, as was the goal of Aethelstan? And what would be the consquences if Britain had been united much earlier under the English, al be it due to conquest.

 

[The Anglo-Dutch Union]

Now a earlier conquest of say Scotland and Strathclyde would have probaly resulted in the Anglifiaction of those areas, while the complete victory of Athelstan would ensure that northumbria's connection with the kings of England would not weaken thus preventing Olaf from ascending to the throne of Northumbria