I found three articles useful in my quest for PCK-knowledge, not all specific to English learning, but mentioning aspects of literacy. In this blog post I briefly discuss them but you should read the original journal articles for yourself, they may come in handy for your 500 word rationale!
So this information is from 2011 but it gives us an idea of how much of the 'iceberg' teachers are using in the classroom. We are all likely comfortable incorporating the first few tasks/activities in our classrooms but we need to ramp up ICT use in deeper tasks to encourage HOT skills. Sourced from http://elearningindustry.com/time-level-use-ict-in-your-classroom