Virgin Broadband Issues

I've had Virgin Broadband for probably 6 years and while expensive I kept it as it was reliable, fast and the white router reached all areas of the house, which I hadn't got with previous providers router. Two people working from home so was willing to pay the premium and not change to get better deals once fibre became available in the area.

Recently the sky box has seen internet drops a bit. Wasn't a big deal as it only affected the home screen and apps as i just change to firestick to stream and everything worked. About 2 weeks ago I lost internet pretty much permanently on most devices. I can see wifi connected but internet just comes and drops ever few secs on the sky box.

Now netflix, disney, prime don't work on the firestick either. No internet connection.

Nest smoke alarms are uncontactable. Sonos speakers are unreachable. Tapo sockets and lights mostly work. Webpages on the laptop and on the phone are unreachable. Everything shows connected to the hub.

Virgin support sent out a new router - Black 2.0 but same thing.

I rang support again and they basically told me do all the usual. Reboot, reconnect network, factory reset and call back. Told me I had too many devices despite nothing new been added this year. I powered off everything apart from about 8 devices.

If I turn on vpn on the laptop or firestick everything works fine. Speedtest is perfect and all sites/streaming work. When I said that to support they said they don't recommend using vpns with Virgin. I laughed and said that must be news to the people working from home. End result was they have to send an engineer out and if I hadn't found my own workarounds I'd have 3 weeks over Christmas with no streaming services/internet and an unhappy family.

I'd be very surprised if its hardware as everything using a vpn works perfectly so can't see the point on an engineer visit. Surely its most likely something with my settings/profile on their side.

Anyone any ideas as I've another week before the engineer calls out?