M&S are decidedly odd.  They have multiple lines of almost identical trousers apart from the material available at once, so I pay for their premium wool/cotton line as appropriate for winter/summer and avoid the nasty high polyester level cheaper trousers.  The trousers are okay if you buy the better line in-store, I'd never buy M&S online.  I've given up on their shirts and jackets as the sizing, fit and quality is all over the place these days it seems.  For trousers they are still useful.   

As you say the waist remains decent and not the hipster fit others are going for these days.