The champions face South Africa, just five weeks after the same opponents inflicted a tournament record 36-0 defeat on them.
But, in one of rugby's most amazing comebacks, England transformed their campaign by defeating Samoa, Tonga, Australia and France - games head coach Ashton claims were all "cup finals".
Despite coming under fire himself following the Springboks loss, Ashton never lost faith in a squad whose experience has shone through during a time of considerable adversity.
He said: "Looking back, we were far too complacent in our approach to playing America in the opening game, and then against South Africa we were outplayed.
"It is a massive challenge on Saturday night and one we are well aware of.
"I understand what a momentous occasion a World Cup final is in any sport, and the fact we are here is probably a massive surprise to everyone around the world, apart from the guys who are here.
"Every player in the squad has been important, and as the games get bigger and bigger you look to the experienced players on the field to step forward.
"They know how to handle it, and they've been there before.
"It is gratifying to have the experience there. These guys have proved over the last two weeks they can control their emotions when it counts.
"We've had four cup finals in the past four weeks. At any stage, we could have been on the way home."
England captain Phil Vickery is desperate to emulate Martin Johnson - skipper in Sydney four years ago - by holding aloft the Webb Ellis Trophy.
It would be an achievement without equal in world rugby, given that no other team has ever successfully defended the title.
Vickery said: "Four weeks ago, we were staring down the barrel of a gun and on the way home.
"But we are in a World Cup final and we've achieved a lot of things to get here.
"We thoroughly deserve our chance to be here but being here is not good enough - we want to go out and retain our trophy.
"I don't think the guys need much motivation. There are huge amounts of expectation outside the team, and from within the side.
"The challenge is for us to up our performance on the biggest stage in world rugby, which is not an easy feat to achieve.
"We all trust each other implicitly within the side and we need to produce a performance that will compete with South Africa."