I saw this thread back in November, where someone was complaining about having high ping spikes: https://community.virginmedia.com/t5/Speed/High-Ping-Spikes/td-p/4870272
I experienced the same issue around the same time. It never really went away, but I think it got a little bit better after a while.
But over the past few weeks or month or so, the issue has returned. Basically, the internet connection will be working fine, and then suddenly it'll become dead slow for some number of seconds or minutes. A speed test will show a ridiculously low (bytes or kilobytes per second) speed, and a ridiculously high ping (10+ full seconds).
Today it has been especially bad, being extraordinarily slow to the point of being unusable. It's at the point where I'm having to go off and make lunch while waiting for a individual, simple text web page to load.
Here's my Think Broadband data from the past week:
What's going on here?