If it is anything like this...
https://youtu.be/ObE1hhOCQ74
Your area is oversubscribed. They have over sold and now have more traffic than the network can handle in your area.
Thats why you (and I) have nasty latency spikes during times of heavy traffic on the network.
Virgin won't consider this a fault unless it gets mega bad, hence the 'I can't find any faults' answer.
Other answer will include...
Turn it off and on again.
Are you using over wifi?
Try changing ethernet cables!
Try connecting just one device.
Try our gadget support service! (£90)
Tighten the cable on the back.
Your levels on the hub are fine so no point in having an engineer visit.
You have two options.
1. Wait for lock down to end and pray it fixes the latency.
2. Change internet providers.