Pakistan's triumph has seen them finally end an abysmal run of 11 ODI defeats on the trot.
Arthur praised the players for battling it out in the field with great determination and self-belief.
"It was just so good to see us go out and play with the belief and intensity that we had spoken about," Arthur told AFP.
Arthur urged Pakistan to show some consistency and sustain their clinical show in all aspects of the game.
"When we put all three disciplines together we know we can beat anybody. We now need to stay consistent and ruthless."
The top-order scored heavily against a versatile England bowling attack as Mohammad Hafeez led the way with a graceful 62-ball 84 to help his team post 348-8.
Pakistan will also be mightily pleased with Wahab Riaz and Mohammad Amir, who returned impressive figures against England and were ably supported Shadab Khan.
"You could see the hunger, the determination and the resolve to do well in batting after a horror show and then the bowlers fought hard, so we need to repeat that in the coming matches as well," said Arthur.
Pakistan have had the upper hand in all World Cup matches against Sri Lanka, winning all seven of them.
Sri Lanka breathed life into their World Cup campaign by edging past Afghanistan by 34 runs on D/L method.
However, they are facing inherent middle order batting inefficiencies, having suffered spectacular collapses against both New Zealand and Afghanistan.
Sri Lankan coach Chandika Hathurusingha emphasised the need for the batsmen to improve their game.
"I don't give pep talks. I give honest talk, that's all.
"I tell them what has to be done. They have to come and perform," said Hathurusingha.
He praised opener Kusal Perera for his aggressive 78-run innings versus Afghanistan, insisting that the left-hander had been given the license to his natural game.
"He's an amazing player," said Hathurusingha. "We have given him the full license to bat the way he wants to bat. We know that when he's come up, most of the time it's match-winning."