I wouldn't read into TBB ping graphs other than as a way of identifying peak time congestion. They are ping packets, they are low priority. If you have issues that you can observe on your connection such as problems with real-time traffic then you need a router that can do proper QoS or to tweak your current settings.
If that was congestion you'd see the blue area getting fatter. If you're seeing issues pushing data through a VPN then try bypassing the Sky router which is probably choking.
If that was congestion you'd see the blue area getting fatter. If you're seeing issues pushing data through a VPN then try bypassing the Sky router which is probably choking.