>   Tuning:
> 
>   When I try to tune to ABC it says it  can't lock (it gets the L_s but
>   not the M).  I can tune the DVB-T device using tzap:

I live in the outer eastern suburbs of melbourne and can receive two copies of TV channels. The second copy of the channels is for the people in the hills who can't receive the main channels but unfortunately because they are higher up in the frequency range they overwrite the main channels.
I can occasionally get locks on the second set of channels (and sometimes the second set are better even in analogue) but some channels are rubbish. What I did instead was to start channel scanning and then abort it before it finishes (I do this on all digital tuners, TV, PC, set-top, etc) and that way I am more likely to be locked into the main channels.
Is it possible you are trying to tune an inferior copy of the channel?