Surprisingly, I've found the Asda own-brand stuff to be my preference, probably because it's got a fair bit of nuts & fruit, and quite big flakes of stuff, rather than sawdust consistency. Added milk powder isn't so bad when eating museli with water (a very small amount, I don't use anywhere near the amount of liquid most people use for cereal), and I suppose if you use milk it just tastes milkier, but if you've used something fruit based, it does not taste right.
Most shop-bought cereals other than plain unadulterated porridge oats are pretty nasty, tbh.
I used to dislike all cereal (and breakfast in general), but then I discovered how much better it all is once microwaved. I don't like the crunchiness, but I really hate food swimming in liquid, so microwaving makes it mushy but damp rather than wet. Cereals better this way: oatibix, weetabix, shreddies, all bran. People tend to think I'm a bit strange for doing this though (especially as I make all of those with water).