prob worth sorting out a BQM from http://www.thinkbroadband.com/ping as thats quite good at giving an overview as to the quality of your connection. You'd have to disable your firewall while you do it though.
Might also be worth going to your hub at 192.168.0.1, don't login but go to its stats and post them here, removing any reference to your wan ip if its shown
The problem is on VM's side. I have the exact same problem, every now and then the internet becomes super slow even when i'm doing the most basic of tasks. It's happening more often now then previously. The worst part is, when I disconnect the power to the hub in hope of refreshing, 3-4 times out of 5, upon restarting the 2 green circular arrows light up indicating 'updating' as I was told. How many times is the hub updated in a month? 20? 1-2 times out of 5, it works beautifully fast. This issue is constant!!
If you are going to suggest to call VM....done it already. Tons of times on the old hub and now maybe 3-4 times with the new hub 3.0. Funny thing is every time ive called I am told there is work being carried out in your area. Literally everytime! So either there is work being carried out 365 days a year, every year or someone is lying!