Hi James,
I have the same USB tuner as you and it does appear as a SONY CXD2820R. I too had a problem not getting the muxes - it just would not work using the ADD DVB BY LOCATION.
To get it to work, I went to the wikiedia page of my transmitter, worked out what the frequency of the muxes were and manually added them instead. It then worked fine.
This is the page I used as I am tuned to the Bilsdale transmitter :
http://en.wikipedia.org/wiki/Bilsdale_transmitting_station
As you can see from this, I added the following muxes :
490.000 MHz 23 100 BBC B DVB-T2
514.000 MHz 26 100 BBC A DVB-T
538.000 MHz 29 100 Digital 3&4 DVB-T
626.000 MHz 40 50 Arqiva B DVB-T
650.000 MHz 43 50 SDN DVB-T
674.000 MHz 50 Arqiva A DVB-T
When I added then, I just chose AUTO for anything it asked for that I didn't understand.
Hope it works for you.
Also a tip specifically for the PCTV stick, make sure you don't plug it into a USB3 port as it doesn't seem to work. Also, just in case you don't know, all the HD channels are on the same Mux - this is great as the way TVHeadend works you can record every HD channel available with just one tuner (TVHeadend is able to record the whole mux).
