I had advice on this but it was several years ago and things might have changed since! I was told that I could not make an application to the CSA as I had an arrangement for child maintenance in place through the court.
However, it would be possible to return to the court for everything to be reviewed/updated.
Many thanks for your reply. Having spent the day trying to look things up on internet I thought that was the case. As CSA have contacted us about this I guess best thing to do is get in contact with them and provide copy of releveant Agreement