I believe I can try PPPonDSS for guided setup as my ISP is one of the supported ones (Optusnet) and I know my way around the bash prompt enough.

There are a few other things I might try too, including lifting a Turbonet card out of one of my other TiVos.

Will report the results back in a couple of days when I get a chance to try things.

Thanks guys, I really appreciate the suggestions.