We've nine phone extension sockets. It's no mansion, just that the builder, like tickmike it seems, was feeling generous.
Once I'd fixed a few issues, I was able to get connection rates some way in excess of what was predicted for my ADSL1 attenuation, and also for distance from cabinet with VDSL.
The issues were...
1) Disconnecting the bell wire made a huge difference. There wasn't any star wiring, just the sheer length of bell wire 'antenna', as it snaked all around the house, was obviously hugely detrimental.
2) One or two of the secondary sockets turned out to actually be masters, with ring cap's. This is not major, and unlikely to have much bad effect, but fixing it can only help.
3) A biggie.. somewhere along the daisy chain, the pair had got swapped. When combined with (2), this gives rise to a circuit whereby each wire of the pair connects via a capacitor to the common ring wire, and hence you have two cap's in series across the pair, horribly damping the circuit. The effect was catastrophic, even dial-up modem wouldn't work sensibly, let alone ADSL!