I know one thing I hope VM keep their international hotspots as we all do so much traveling these days don't we ha ha.
I mean if they become part of telefonica I see free international calls, texts and data or at least i hope so.
Orange / EE both work extremely well with the VM virtual network when moving around different countries at the moment while they use the EE network.
I know the Vodafone sims which virgin are now offering are not great in europe as they are paired with SFR (know for being the worst network for service and customer service, worse than virgin media(might be why they joined forces(to spread the misery)))
I guess we will see what happens I know i'll notice any changes that are made from frequent traveling (you know its a sign when border force know your name before they even see your passport).