I've had no choice (unless I wanted to buy my own) so I've gone with Tiscali router (Speedtouch) and TalkTalk router (DTech), obviously all prior to TT taking over Tiscali.
The Speedtouch gave adequate connection via Tiscali at somewhere in the region of 1.6 mbps.
The DTech forever dropped speed and had to be rebooted. When it was good it gave c. 4mbps. Tried another DTech and it was the same.
I reconfigured the Speedtouch with the TT settings and that has been great, consistently returning 3.6mbps and hasn't been rebooted in 6 months.
I don't expect much more than 3.6mbps from my exchange as I'm 2 miles away, but the exchange has been LLU'd which influenced my choice of TT in the first place.