I've contacted my ISP to ask if they will be providing them, if not they are only £10-£14 online. My ADSL connection of "up to 8MB" only achieves around 1MB so this is something of great interest to me. I also fall into the criteria where it is supposed to work i.e. router attached to extension wiring.
I have just ordered one from click here and am awaiting its arrival. This was the cheapest supplier I could find. Will post back to the forum on how successful it is after installation and allowing time for ADSL to resynchronise.
there are various sites that show that once you have adsl and the filters you no longer need the wire in terminal 3 of the master and slaves. If you have the modern BT master remove the bottom section and unplug it from the master socket. Look at your extension wires on the removed section and if you have a wire or wires in terminal 3 remove it[them] do the same in all the slave sockets then fit the bottom section back in the master socket. Mine went up from about 4 to 6.3 MBPS after removing the wire. I doubt that the Iplate would get me anymore on my upto 8 MBPS service.