Trust me you where not getting that speed, to get a 100mb connection on a domestic line is just not going to happen in the UK we haven't got the hardware on the D side equipment in the exchange for it let alone what your claiming. A cheep leased line connection in the UK for a 100mb service
is at least £800 a month and that is under a set of circumstances limmited to the back end provider having a point of presance at the local exchange and being within 1000 meters of said exchange after that the price sky rockets.
You are taking about a coaxial connection, which in theory can support upto around 150mb speed but to get that you have to be prity much the only person on the loop and have a Docsis 3 service and the CPE to support it, virgin are still in the process of moving from Docsis 2 and there is one small area of london that can get the 100mb service and even then it's unstable.