"The team had a very good mentality at the weekend after we lost two points at home to Aston Villa, and it was a fantastic result because it is not easy to win at Manchester," he says.
"If we had taken just one point we would have been happy, but it is not finished, because there is a very big game against Arsenal on Saturday and if we don't win that the victory over Manchester United will have meant nothing.
"I think we will need the same mentality - we play very well but sometimes not with our heads but with a bit of concentration it is possible to win.
"I know they have some fantastic French players but West Ham play much better when they play teams like Arsenal, Chelsea, and Manchester United, so there is no problem.
"I hope we work very hard for the rest of the week to beat Arsenal."
"It is very strange but I am happy about Saturday because not many French people win there, and I have played twice and won there.
"In France everyone says 'never two without three'.
"Maybe they are the best team in the world in the last 10 years, but I repeat that it is not finished and we need another win."
Talking of the exclusion of David Beckham from United's starting line-up on Saturday, Seb says: "Everybody was surprised but Manchester United play 50 times a year and that is too much for one player.
"He had the World Cup and Champions' League games as well but everyone knows he is a fantastic player."
But he certainly wouldn't want - nor does he expect - to be 'rotated' himself, and he adds: "I am not the same level. I play every game because I'm not a genius and West Ham doesn't have lots of players.
"In my position there is just me now Rigobert Song has gone but that is no problem - I love to play every game."
He feels he is settling in both on and off the field and adds: "I want to speak English because I feel English; everyone is nice and we have some good players so it is easy for me, and I want to prove something every time.
"Everyone in France knows West Ham now and is saying I am playing very well - they want me to come back to France but this is not possible because I love West Ham too much and France is in the past."
And, although he didn't speak to compatriot Fabien Barthez after the game on Saturday - though he did have a brief chat with Silvestre - he is backing France's number one to bounce back.
Says Seb: "Barthez is the best goalkeeper in the world, and he is just having a bad time."