"I will go there, I know," he says, while adding there are just one or two minor details to settle.
"Glenn rang me personally, and that was important because it showed a mark of confidence in me.
"As I said from the start, I want to be the best right wing back in the country, and I think I can do that under Glenn."
Sebastien says that there were no shortage of offers to Metz for
his services, adding: "Middlesbrough, Manchester City, and
another big English club were after me
and there were also bids from Marseille, Bordeaux, and Sedan in
France.
"But my priority was always West Ham, and that is a sincere statement because they are in my heart.
"I told Glenn that, and I hope to finish my career here working with Glenn, this club, and the supporters."
Sebastien's personal admiration for Glenn is obvious; and the feeling is a mutual one.
It was Glenn who tracked his progress after the two teams met in the InterToto cup and recommended him as a loan signing when Trevor Sinclair and Steve Lomas got injured.
"It's extraordinary that he has become boss," he says, "as he is like a second father to me.
"I have a relationship with him that I have not had with any other trainer.
"He has always advised me and been honest with me, saying that I am a good player."
He feels criticism of Glenn's appointment is unjustified, adding: "Everyone has to start somewhere; there is a manager called Elie Baup at Bordeaux who was less well known than Glenn, and now the top Italian clubs and Monaco are after him.
"I think Glenn can be a big success especially when you think about the quality of players we have here.
"I will do everything I can to help him."
Sebastien also reveals that fellow countryman Fredi Kanoute is happy with the appointment, adding: "The critics can stop because I know Fredi will stay.
"I have spoken to Fredi and he says he will stay.
"Why? Because Glenn is the manager."