Hi Sarah, you're having an issue that is affecting loads of other customers. Log onto your Hub (Go to 192.168.0.1, you don't need to log in, just click on "Check router status"). Then click on "Network Log", and I guaruntee you'll see a bunch of T3 error log messages.
T3 is an error code to indicate an error between your hub and the "terminal", which is where your line connects to Virgin Media's access layer.
The first thing you should do is open an official complaint: https://www.virginmedia.com/help/complaints
Virgin Media don't bother themselves to fix anything until your complaint gets to the Communications Ombudsman, which takes 8 weeks. I am sorry to say that you will probably have technicians come to visit you who will do absolutely fanny all until this case gets to the Ombudsman.
You should use this next 8 weeks to collect evidence that you are being regularly disconnected. Also try doing some speed tests by https://samknows.com/realspeed/ and check if the speeds are dropping below your minimum speed guaruntee.
But yeah basically don't bother with customer support, do the official complaint as that's the only way to get it escalated.
DO NOT MENTION WIFI. Make absolutely sure you always specify that this is happening over ethernet and that you've tried 2 different cables, and 2 different devices. I'm sorry to say that you're going to have to wait 8 weeks for this to get to the Ombudsman before they send anyone who can fix it (they prioritise escalated cases).