I'm not a knowledgeable person when it comes to stats, but I do know it would be pointless chasing PN to tweak your download speed. There's not much they could do without getting an engineer out and if there is no problem you could be liable for a charge.
There's no point comparing what you had on ADSL to what you get on FTTC, as one is from the exchange and the other from the street cabinet. FTTC degrades much quicker over distance than ADSL does.
If you had far more detailed stats (
see here) with graphs it may be possible to tell if you have any problems with the line etc.
I currently get around 50 down, but only 4.2 up (at one point I had 12 up!) and I'm 450 to 500 meters from my cabinet, it varies so much depending on quality of line, interference, crosstalk etc. They also use power masks on FTTC to protect ADSL signals, and how much these masks affect your connection depends on how far the cabinet is from the exchange.