To answer your question....
Speeds are most likely dipping between those time due to them being the busyiest times of day for people going online and streaming and using the more bandwidth on the network.
The local network in your area may be suffering with over-utilisation, basically congestion, you can if you hang on here I'm sure somebody from the Virgin team will have a look at the network and confirm if this is the issue or not.
In the meantime, you could copy and paste the stats found at 192.168.0.1 click router status (don't login with password unless required) then copy all information from the tabs marked Downstream, Upstream and Network Logs, this will help is check if the signals coming to and from the hub are correct and help diagnose the issue faster.
🙂
If I've helped please let me know
🙂 Matt
A 10+ Year Virgin Media veteran, been here through the Up's and the Down's and Down's....
Vodafone 5G EE BQM Hub 4 BQM Hub 3 BQM Hitron CGNV4 BQMTechnical Support - AV & Networking - Customer Service - Finance - Culinary - Construction