The reigning world champions looked down and out after the Springboks humiliated them, but successive victories over Samoa, Tonga and Australia have revitalised their campaign.
If they can defeat France - repeating their semi-final success over the same opponents in Sydney four years ago - then South Africa or Argentina will await them to contest the Webb Ellis Trophy next Saturday.
Ashton said: "I think there is a heightened sense of anticipation among the players, and it is going to heighten even more.
"The important thing about anxiety is that it is okay, so long as you convert it the right way on the field.
"The side that controls their emotions, especially in the first 20 minutes, will go a long way towards winning the game."
England have already played France three times, losing back-to-back World Cup warm-up games against them, but Ashton is keen to stress the one-off nature of the contest.
He added: "You pick up bits and pieces out of all the games, but it is such a one-off on Saturday night that what has happened this year is an irrelevance.
"You don't have such a game come along very often, and we are treating it as a one-off Test match.
"We've talked about how we want to attack, how we want to defend, but what if France don't play the way we have planned for them to do so?
"The players need to be adaptable on the field."