This highlights something that is unnecessarily complicated for a seller, I think. In an ideal world, your seller account on eBay would know what you wanted to do, and do it. It wouldn't take much rethinking of the coding for the changes to be swept through your entire inventory, so that the different-postage-method-nightmare would not happen.

I will metaphorically keep my fingers crossed that you'll see an increase in the bulk orders that were dragging their tails...