Originally Posted by MattP
You will not be charged as long as you are logged in to the same account that made the original purchase. Please note that the multi-pack and individual episodes are considered different products. So make sure that since you bought the multi-pack originally, that you buy that again and do not try to purchase each episode one at a time.
Thank you again. I tried and indeed it said that I can download the content for free since I already purchased.
Summarizing Matt's latest support mail, it's important is that
a) you are logged into the same iTunes account with which you originally purchased.
b) don't tap buy on episode 2 if you originally bought the multi-pack. iTunes is not smart enough to know that one is part of the other. If you choose to buy it, it WILL charge you for the episode. If you originally bought the multi-pack, tap on the multi-pack, even if you just want to download episode 2.
c) you still get the question if you want to buy for $/EUR xyz no matter if you bought already or not. You need to tap Buy here, even if it seems to indicate that your purchase is not known to iTunes.
d) THEN, AFTER tapping Buy in the first prompt, you get a prompt stating that you already bought this item and asking the slightly stupid question whether you still want to download it for free… Tap OK.
e) THEN, the "buy" button next to episode 2 changes to "get". Tap to download episode 2.
Maybe this helps one or the other.