NP.
MTU/RWIN are not set in the router pages.
http://www.dslreports.com/tweaks : Follow the instructions for the java test applet. MTU should be 1500 for ntl.
BTW - you've done the usual security stuff for the WiFi, yes? Changed the default 'admin' password on the router, and set the encryption to WPA-PSK. Forget any other nonsense like hide SSID, MAC or IP filtering.