@Saoirse, I assume it automatically becomes a renewal.
I've looked at my ikamet book.
My previous permit was 25.11.2010 - 24.11.2011.
Before it expired I did all the paperwork and in the back of the book is written:
Renewal 24.11.2011 - 23.05.2012. Extended until 23.05.2012
Your residence permit number stays the same so they will be able to track your previous records.
Go check with the police station but if you're back in Turkey one week before it expires, you can just use up the three months of your tourist visa and then apply again.