I have FTTC, maxing out at 40/10. My unlocked VDSL router shows me on Profile 17a with a max of 54/15 possible
If I take my VDSL router next door to my neighbour (he also has FTTC) it shows a max of 75mb/28mb - quite a sizeable difference. His db stats, etc look much better.
What would be the best plan to get BT to improve my line - obviously there's isn't a fault as such but the line is considerable poorer and perhaps a cable swap to the cab would sort this out.