I just solved my problem!
Since installing iOS6 I immediately installed and started to use a third-party camera app for most photos. Occasionally I would use the default camera app for photos - but only through the lock screen.
So, it turns out that you need to open the default camera app through the icon at least once. This brings up the request to use location services, and also adds the Camera App to the Location Services list. Solved.
For some reason, using the camera through the lock screen does not trigger this request for location services, and every photo taken is naturally taken without any gpsinfo included.
A simple answer to what seemed like a complex problem. Glad to find the solution though. Hope this helps others.