I’m actually based on Ireland and here we only have Vodafone with NB-IoT network. As far as I managed to get information, they are allowing access to the network only with their own SIM cards. I tried to get. V-Sim Card from Vodafone, but those don’t allow access to their NB-IoT network.
So we will need to wait until they start allowing NVMOs like Hologram access to their NB-IoT network, or unless they start selling the NB-IoT SIM cards directly.