Thanks shroomgirl, I think I'll stick to making home made butter rather than purchase, I have used those butters in the past. I'm sure others will agree there is much to be said for fresh home made butter.
I have found salted butter has more salt than nessary for a baking recipe. It tends to make too salty a batter even deleting the salt in the formula.
Salted butters tend to be lower in quality because the salt is masking impurities.
Stick with unsalted, it is much easier to use than trying to calculate the amount of salt you need to subtract from a recipe. Most recipes I believe use unsalted butter for this very reason. Also it is almost impossible to know exactly how much butter the manufacturer adds.