Thanks for posting and a warm welcome to the community.
Sorry to read that you are experiencing packet loss and lag spikes.
From checking your connection, there is a high peak time traffic fault in your area. Our networks team are investigating the problem and are improving bandwidth and performance to help with this issue. The reference number is F004496785 and with a review date of 11th January.
Wired connection via PC - the service is appalling with a less than helpful call centre who do no more than reboot the router and tell me "its because other people are using Virgin and it's to be expected at busy times" !!!
With the packet loss/slow speeds during the evenings this will be due to the high peak time traffic fault in your area.
Considering the equipment you have with the level of broadband service, I think it is best to give you an up to date router, however this won't change the overall effects of the fault. I've sent you a PM (purple envelope icon, right corner) requesting some details.
I've cancelled my account. Gone to BT infinity. No lag spikes, no packet loss, low contention and they guaranteed minimum speed in writing. Ohh - nearly forgot - it's cheaper. All you have to advertise is fastest broadband, speed matters little, you can stream 4K TV on a 2Mb connection! Quality of signal is king.