Both B.I.G. on announcements, but don't live up to it
I've been a customer of both VM and BT, and their networks are plagued by congestion/traffic "management "(BT) and packet loss (VM) in quite a few neighborhoods.
In particular, VM's consumer forum is littered with people complaining about the issues and their dates for "fixing" this is shifting every time someone requests info from them.
I was an Infinity Option 2 customer for 18 months prior to just signing with VM last month, and even though they don't have packet loss (which kind of makes a non-traffic managed 100mbit connection useless), the connection got "managed" down from 36m down/8.5m up all the way to 7m down/2.4m up during peak periods - every day.
Oh, and BT don't tell you you have to pay them £30 to cancel Infinity - it's apparently in one of the many pages of fineprint attached to the ordering process but never is it mentioned unless you attempt to give them the boot.
Regardless of what the connection speed is, these companies have serious network infrastructure issues, and they are not really pushing the boat out on getting their routing and switching infrastructure up to the job of serving all of us existing customers - no - they're just adding more "high-speed" pipes to an already clogged system.