It was my understanding that on a typical VDSL service interleaving would not be switched on as line length should be short enough not to need it, but I suppose it depends on the ISP and how far you are from the cabinet.
Does anyone know what sort of line length might use fastpath?
Would be interesting if those with fttc could do a speed test and measure thier line length to the cab using google earth, if it's running along poles it's easy to do otherwise go by road or line of sight, hopefully being around 300m means fastpath is used.