With noises being made by the authorities about the actual against the advertised bandwidth achieved by broadband connections, it's worth considering how much bandwidth is enough bandwidth for internet TV.
A very good image can be achieved with 1.8Mbps VC-1 streamed video (ie Windows Media); Flash comes nowhere near this quality at the same data rate, but the addition of the H.264 codec will fix this.
Beyond this data rate, increases in quality require large jumps in bandwidth. HD internet TV is considered to be around 8Mbps, but in reality this is far from being a true HD image.
So, let's say 2Mbps. To make sure that you achieve this with contention, a 4Mbps broadband connection is necessary, and if you have two PCs in the house, then 8Mbps makes sense.
Connections at 100Mbps or more are available in Far Eastern countries and US providers offer 25Mbps connections as standard, but I can honestly see little benefit in going over 8Mpbs unless you are also buying an IPTV service, which is likely to require better contention and multiple streams to feed PVRs and multiple screens around the home.
The major issue is not how much, but how reliable. So, Ofcom is right to look into this issue and should make providers publish an average connection figure from an independent third party source as well as the theoretic figures in their marketing.