Working time regulations is about preventing companies from using their excessive bargaining power on a tense job market in order to get the most desperate work

Working time regulations is about preventing companies from using their excessive bargaining power on a tense job market in order to get the most desperate workers accept anything. You can be against it (I'm not), but it's another topic from part-timers vs full-timers. Regarding wages, it's normal that you make more (ceteris paribus) if you work more. As for promotions, I guess it depends on the kind of role involved; many managerial roles are known for requiring pretty long hours, so this might not be compatible with 32-hour week for a start. But you should be able to move up from, say, junior to senior dev if you got the skills, whatever your working hours. Everything is not possible obviously, but when it is, mere working hours is a pretty lacking metric for merits and promotion--as the article points out.