Is it possible to enrol with CSU if I have yet to complete IECL Level 1?

Yes, as long as you have an undergraduate degree, you are more than welcome to enrol in CSU and IECL Level 1 concurrently or you can start at CSU and enrol at IECL later. If you do not have a previous degree/s, you will need to complete IECL Levels 1 and 2 before you enrol with CSU.