You cannot reasonably build an ISP network with single /64. RIPE assigns /32s to LIRs and LIRs are supposed to assign /48s downstream (which is somewhat wasteful for most of kinds of mass-market customers, so you get things like /56s and /60s).
As I said, "should". In some places there will be enough people in the chain that won't be bothered to go to the LIR directly. Think small rural ISPs in small countries.
