Originally posted by grayboy amen to that!
Thanks everyone, it was my misunderstanding completely - I got it into my head the custom setting was referring to the AF Button - which is what was confusing me. All makes sense now. Although - why would you want to select a different focus point? I have it on centre point, and if the point of focus is off centre I focus on my subject and then frame the shot while still holding down the shutter release. Which seems to work - or have I got this wrong as well?
Well, the issue is that when you focus and reframe, if your depth of field is narrow, you can shift your focus slightly and end up with soft photos. If you use one of the side auto focus points, it can let you shoot without reframing.
I personally use option 2. I was quite used to the K20 and K10 which allowed shifting auto focus points without hitting the OK button and I was constantly bringing up menus when I wanted to shift auto focus points.