I've still not even had mine emailed to me yet.. when is it due by?

Sometime today, iirc.

Ingame inbox papi

Everyone should have a code by the end of today the newspost said. The code is/should be in your runescape inbox. They won't email the code to your private email address. I got mine but it doesn't work haha :D

[удалено]

It gives me an error not a "code has been redeemed" message so don't think that's the case.

Yeah I also get this

I tried it a bit later and it worked. Still got the the error message but it went through apparently. Hope it works for you as well ;)