If you are really 7km from the exchange, and you are getting 2mb sync speeds, I would be pretty surprised. On a 63db att, I would be surprised to see anything above 1 meg, which is what you are currently getting, but I guess it depends on the quality of your copper, pairs etc
Maybe covering old ground. but I am assuming the PSTN line is ok (no noise, crackles etc)? If not, that should be your first point of call, especially if the line is a long one.
Lowering the SNR may work... If I were you, I'd contact your ISP, ask them to request an SNR reset (I am also assuming this is on the older 20cn network). That should reset and recalculate the SNR for you.
If that doesn't help, you could ask your ISP to log a long line fault with BT. That will usually result in an engineer who should come and check the line, all the pairs, check e and d side for errors and maybe lift and shift it in the exchange. It should be noted that the ISP may ask you to check your kit before raising the engineer, as it is possible a faulty router can cause the rate you sync at to drop, but it isn't very likely
If that doesn't work, there ain't much more you can do. As DSL is not guarantee'd, it can be a real pain to get BT to do anything, especially if there is only 2 properties on the line. It may be a case of like it or lump it
Hope that's some help