The way around this that i have potentially solved and has worked so far but obviously wont be possible if you have thousands of items listed is the following :
Revise all your listings, you dont have to change prices etc as your original price should appear in the revision format. The 20% only seems to appear when you see your listings from a buyers point of view. Scroll down your item in revision format then click on revise with displayed fees or it may just say " save it " . Give it a few mins or more to update and the 20% should have been removed from the listing and postal price
