Technically, this AST is still open, which might explain the lack of info in the archives. I've been looking for the actual requirement for years but aside from passing mentions in documents in Kew, have failed miserably in that task (it's on the grail list). It was also intended to replace HAWK in French service, if not others.
It evolved into MSAMS, FMS and EURSAM with various missile systems put forward over the decades.
I have a feeling that it was put on the back-burner when the remarkable CAAM family came on the scene.
Chris