Just to update that I'm not much further on. Here's a summary of what I've tried to-date:
I have no spare power cables in my case so I got an adapter cable & manged to hook-up one of the molex connectors on the TBS supplied power cable. Bingo- for the first time I got a signal on the previous "No Signal" channels
...... for a while.... then the "No signal" message came back..... then I tried a restart & then no channels worked.
Even more confusingly, as above all channels work fine in other software (DVB Dream & TBS Viewer), all channels can be recorded fine but report "No Signal" in WMC Live TV & when in "Edit Channels" the "show preview" displayed all channels fine!
I was convinced that I must have a corrupt MC TV Set-up, so I tried a MCERecoveryTask, which reported a "Last Run Report" error of "0x80040154" in Task Scheduler. So then I tried the Hack7mc method to clear the Guide & Tuner Set Up. Then I tried turning WMC off & on again under Windows Features. None of these attempts have produced solid TV.
My last thought is to go back to the power issue- perhaps all 3 of the molex connectors on the TBS power cable need to be connected? I am using a pci to pci-e convertor, perhaps it is not passing through enough power? But don't really want to buy/connect up another 2 of the adapter cables I bought, maybe I can use
http://i.ebayimg.com/t/4-Pin-Molex-to-6-Pin-PCI-E-power-adapter-converter-graphics-card-cable-/00/s/Mzc3WDUwMg==/z/-LcAAOxyd8NSa6Ph/$(KGrHqJ,!rQFJrC8BN8EBS,6PhS61w~~60_12.JPG instead of the TBS power cable? Maybe the card itself is faulty? Would an older driver work? Any help?