To connect computers to the Virgin Media WiFi network, the same security certificates would also need to be installed, but that requires more detailed technical knowledge to complete than on mobile devices using the app, and isn't always possible for corporate computers etc.
So Virgin Media have focused the service on those devices that are most likely to be moved around and used on the go i.e. Android and iOS mobile devices, and also where those devices have a simple and easy setup.
This would be fine if Virgin published instructions on how to use that security certificate on a router or PC, it is technical but if you did it people could copy it.
The basic process is to extract the Enterprise key, Virgin could easily create a VPN config as an export from the App to work on different platforms, so that that a config file could be exported and for say Windows click on a .reg link to add the config to the device.
Even if VM did not do that they could give some parts of tech solution.
Alternatively do as BT do and provide a captive portal for an unsecured network used at customers risk.