[FTTC] - Hitting a 20 Mbps barrier and wondering when the trail is ending.

[#1]

I seem to have been consistently hitting a 20 Mbps downstream upper limit in my tests over the last few weeks.
Is there any form of profile lock in place?
My current Gateway is thn-ag1 in Telehouse North if this helps (although I'm sure you could work that one out in one glance at my profile).
Also, out of interest, how long is the estimated end of the trail away? (if that's even answerable at the moment).

[#2]

Oh, and on another note, would you like me to ship back any of the older routers you've sent me so far?
They're all in their boxes in a plastic bag marked 'Fibre Trail' in my garage if you do...

[#3]

And on another another note, should I change my interleaving setting to 'OFF' or leave it as on in the connection settings section under My Account?
Just curious as I'm assuming the problems with stability caused by long line lengths are somewhat reduced by the use of the fibre to the cabinet across my street... Perhaps, however, I am wrong in my thinking.
It is set to 'ON' at present at any rate.
Hope you had a nice holiday time Dave et al; and I wish you all a cracking New Year!