Apologies for not coming back for a while, but I've been keeping an eye on the issue. So, the issue is not all VM hotspots, it seems to be mainly ones in residential areas and even then it's not all of them. However in the area I live a good number of them on routes to either public transport or to the shops do. I notice it as if I'm streaming music it stops and when I look at the phone I see the login prompt for the hotspot. At least I know it's not my phone but the hotspot network itself.
It’s always best to be positive but we all have crappy days.