Just had my BT Infinity installed this morning. Great engineer that did the job, changed an extension socket to a master socket and screwed the BT modem onto the wall so it looks very neat.
I'm about 400-500 metres from the cabinet I'd guess, the estimate was 29.3meg down and 7meg upload from the BT checker.
I'm syncing at the full 40/10 and the engineer let me look at his checker that tells you the maximum the line can support which said 63meg down and 20meg up. Sounds promising for the future, especially considering the distance to the cab.