I'm having an issue whereby different devices are getting different speeds on wi-fi. Strangely, they all report similar download speeds (~50mbps) in various speed tests, yet when browsing and downloading, two of our devices are painfully slow compared to the others. Downloading a 3mb app from the Play Store will take minutes on end, whereas on other devices it'll happen instantly.
One thing to add is that the issues are on new devices, I bought the new Google Pixel phone yesterday and it's having the issue, as is my partner's Nexus 5X, yet my old phone Nexus 5 and our tablet Galaxy s2 have no problems whatsoever.
I don't know whether this is an issue with Virgin or the devices but I've checked all settings across all devices and there's no obvious differences in how they are set up.
Are the devices connected to the 2.4Ghz or 5Ghz WiFI networks? Try connecting to the other network to see if that makes any difference. If using a Hub 3, you'll have to log in and change the network names as the two networks share the same name by default.
My Nexus 5X used to dislike something about the Virgin SuperHub's 5G network, it would only work reliably on the 2.4Ghz network. Once I switched to my own router the problem went away.