Interesting, my two ISPs (one in Belgium, one in France, not business ISPs) hand out fixed /48 blocks to every customer. As far as I know, that's what RIPE recommends, they actively discourage from assigning longer prefixes than /56.

The modems they provide handle it without needing anything special from the customers. The devices get IPv6 addresses from this prefix, and are firewalled by default. It's pretty simple so I'm not sure what could go wrong there.