There are 2 thing out there at the moment, the BT I-Plate and the old faithful NTE 2000, both will help any ADSL line which has extension wiring beyond the NTE, if there is no extension wiring beyond the NTE then a good quality filter is just as good. It is also worth noting that the NTE 2000 was always an engineered fitted product and was never for general sale, it's my personal preference but does limit the use of the router at the NTE location.

You can also boost the speed without spending any money at all and disconnect the ringing circuit, labelled as 3 on the face plate, most plugin filters don't need that to be connected to ring anyway. If you have an I-Plate or NTE-2000 then there is no advantage in most cases of doing this.

Edit - In over 50% of cases I would say that broadband faults are within the home, and this is after the SP has done all the testing etc...

Cheers

Cris.