In Melbourne the cut off is the end of April. There is a trend at the moment to hold boys back a year if their birthdays are between January and April.
as an example, in my DSs kindy class, there are 2 boys who will be not-quite-5 when they start prep and 3 or 4 who will have already turned 6.

Did your kindy teacher give you feedback on what they thought would happen? We had parent/teacher interviews a couple of months ago where this was the main topic of discussion (which seems crazy in some ways, but school enrolments needed to be in by July). In our particular interview the issue of pens and pencils and not wanting to make pictures was raised - so we have been working on that, and it looks like he'll be OK. You should be able to make an appointment for a detailed discussion with the teacher to look at whether he is ready (and if not whether you need to consider repeating or whether you need to work on some issues instead).
Yep we have an interview in October. From reading all your helpful posts Id think he wud benefit starting a year later