My ISP (Andrews and Arnold) does exactly this. https://support.aa.net.uk/IPv6 https://support.aa.net.uk/IPv6 "Customers are allocated a /48 block of addresses

My ISP (Andrews and Arnold) does exactly this. https://support.aa.net.uk/IPv6 https://support.aa.net.uk/IPv6 "Customers are allocated a /48 block of addresses - this is usually per customer, and so a customer with multiple circuits or sites will have a /64 allocated from the larger /48 block"