I had pretty much the exact same dilemma just last weekend, so I can definitely help you...
So I'm stood there in the milk isle at my local supermarket, which so happens to be Sainsburys, it's decent but a bit pricey on some things.
Anyway, I'm lookin at this milk and I'm thinking should I get semi (lol at semi) or skimmed, I'm trying to lose a bit of excess weight so thought the skimmed might be better. As I reach to grab myself a 4pinter of skimmed, what do I see?!! I see a 2% fat milk with an off orange coloured lid!! This confuses me massively! I pick it up with the skimmed, read the nutritional value labels on the back, and to add confusion I can't for the life off me work out which one is better for you, they're are pretty much exactly the same!! So I sack it off and go get some cheesestrings instead.
I think what I'm trying to say here is, life is good if you have a Nectar card mate.
You're welcome