ALl i can reccommend is to take it back to court with all your evidence of his non-attandence and go from there. It is a long winded way, but from experience, its the only way. I'm just on the point of starting this procedure myself with my Stepsons Bio mother who failed contact.
Sadly, you dont get to decide if your ex has a custodial sentence - thats up to the judge and 99% of the time its a slap on the wrist.
Seek legal advice - try the legal aid route - try here
http://www.clsdirect.org.uk/legalhelp/calculat or.jsp?lang=en
Good luck
Flower xx