First of all, what is the "sensible" site? It is probably one of the many "anti" groups with somewhat radical ideas
Secondly I assume you are thinking of going to Hamm... this is NOT in Hamburg, but the actual town of Hamm (dont want you ending up in the complete wrong place!)
At these sort of shows it is basically "buyer beware" - you should be aware of what you want to buy and dont rely on the labels on the pots to always be correct. It is a VERY busy show so if possible rerserve your animals and advance and just pick them up at the show. This will save you looads of time and you will be more likely to get the animals you want.
Bringing them back is easy enough, you shoud have a receipt and any CITES paperwork where relevant, the customs officers are a bit clueless so you may have to fight your corner with regard to it being legal for you to bring reptiles back. Most snakes are brought back in poly boxes and/or cloth bags.
Welfare wise Hamm is quite strict about how the animals are packed/held/sold, for example I seem to recall people being asked to remove stock from sale because they werent individually packed...
The only thing with Hamm is there is quite a lot of wild caught stock which some people dont find acceptable.