Got my offer. Glad I rang HR Connect today. Apparently, my offer letter was sent out on the 13th. I hadn't received it, thankfully when resent it appeared... but also the woman was able to note on my account that I should have an extension for my reply.
Bit annoyed about this as the start date is a lot closer than it would have been if I had known last week and I have a 4 week notice to work.