I don't use eBay labels or C&S. I don't use a printer enough to warrant having one, even though they are dirt cheap these days. I have owned a few printers in the past and they got used so infrequently the inkjets would clog up and not be able to be unclogged. 

The parcel should come in at under 500g (assuming he doesn't buy any more than what's he's already bought / bid on. Most of it is small stuff). I have to go to the PO today, I'll get them to show me the express satchels for a comparison. If they are the same size as the regular satchels, I don't think the box I'll use would fit into a small one (a couple of the items need to be packaged well so a slightly larger box is needed).

If they can just stick express tape on it, that might be an option too. Although I think he's now got the idea to finish buying before he pays. He's only got 100 feedback and exceptional feedback at that, so I think he was just trying to be a good buyer, not realising the possible implications of multiple purchases and combined postage.