Hmm... I'm not 100% sure about changing up, but I think it doesn't when you're in M mode. However, it does change down for you, which can be handy if you pull up at a roundabout and forget you're in M, but it can also be annoying because if you brake coming into a roundabout for example, the 'box might drop down a gear for you at the same time as you push the paddle to change down, and you end up dropping down 2 gears and losing count of where you are. Maybe I need to practise more, but I couldn't really get the hang of it, and now I only use M mode when I'm on fast straight roads - I find DS is best for tricky junctions, roundabouts, overtaking etc., and it does a pretty good job.
2012 F10 520d M-Sport, Sport Auto, Imperial Blue, Black Dakota, Sun Prot Glass. V-spoke 281 Winter wheel package
Previous BMWs: 2009 E92 320d M-Sport, 2006 E92 335d SE, 2004 E60 530d ASE, 2000 E39 525d SE, 1997 E39 523i SE