'Cultured Buttermilk' and making Ranch Dressing

So I brought with me the powder mix to make my own Ranch dressing. It requires buttermilk, but the only thing I found at Sainsbury's is 'cultured buttermilk'. From scrolling through the threads here, it appears that there is a diff between buttermilk I'm used to and this cultured buttermilk. Do you think it would be ok to use this to make the dressing?

Not sure if this will help but we used to bring over the hidden valley powder and make our own often and mixed it with equal parts of mayo and milk then some of the mix.  the more powder we put the thicker it became- more like a dip.  We used to get the large 16oz container from Sam's so I'm not sure how much is in the packet or if we were really doing it wrong

I've mixed it with creme fraiche before - for a dip, but that ends up really thick...suppose you could thin it with a bit of milk?

I know in baking you can substitute buttermilk with 1 cup of regular milk and 1 tablespoon of white vinegar or lemon juice.  I've when baking things before, but you might just want to go with the mayo or creme fraiche...
http://frugalliving.about.com/od/condimentsandspices/r/Buttermilk_Sub.htm

What I've brought with me is the 16oz bottle of Hidden Valley Ranch powder from Sam's. The instructions say to use equal parts mayo and buttermilk. I've not really used buttermilk in anything so I wasn't sure what I could substitute for it. If I decide to make my own, what milk should I use (1%, 2%, etc?). We only drink .1% skimmed milk, so would that work as a substitute?

Do you think it would be ok to use this to make the dressing?

Absolutely fine. I use UK buttermilk in cooking all the time.

I've made it with 1% skimmed milk in the states and semi skimmed here (not sure what the exact percent would be).  

We always did the powder/ mayo mix with whatever we had in the house- usually skim.  I've also done cooking with the milk/vinegar mix with both whole and skim milk and couldn't notice a difference

Just thought I'd update and say I mixed up the ingredients, and the dressing is yummy scrumptious!  Can't wait to put this on my baked potatoes!