I was contacted by a Virgin Media salesperson just before Christmas and offered an upgrade which included improved broadband and a Volt SIM card, which would give me all the O2 benefits (cinema ticket, Gregg's sausage roll etc). The SIM that we've been sent is a Virgin Media one, but despite putting it in a phone we're unable to log into the virgin media app with it (or my own details). I've also tried the O2 app, but this doesnt work either.
Concerningly the O2 website advises that it should be an O2 sim (even with Volt) in order to get the O2 benefits. I'm hoping this isn't the case as much of the salespersons push was around the O2 benefits (quoted them a number of times).