In the new issue of Norwegian jazz magazine Jazznytt (nr 06/2009) they have a six page presentation of Fred Frith, with an interview done at the Kongsberg Jazz Festival (summer 2009). Frith talks about his relationship with Robert Wyatt, and says that as a student he used to call Wyatt and ask if he could join Soft Machine! He was invited to to play on "Rock Bottom" og "Ruth is Stranger than Richard", and this later led to working with Ivor Cutler and Brian Eno.
He also seems very fond of his partners in Henry Cow, Chris Cutler, Lindsay Cooper and Tim Hodgkinson.
If you follow the link to Jazznytt, you may read the whole issue in PDF, until a new one is out (I believe). But be warned, it´s in Norwegian.