I know this is an old thread, but I am about to try almost the same setup as I'm switching ISP and likely to have a spare Speedtouch 780 which I have been using for VOIP. The new router is for FTTC and doesn't have any VOIP ports.
I managed to locate the templates mentioned above at the modem forum (link below)
http://download.modem-help.co.uk/mfc...ata_7xx_WL.tpl
Not sure exactly which steps need to done next, so any pointers appreciated.