I've had a couple of TVs now that allowed direct HDD recording, but I've always preferred using a PVR. I can't speak for the C9 specifically but, in general, I think you're always going to get more functionality from a dedicated PVR than recording directly to a HDD from a TV.
Probably the most important aspect is the ability to record one channel while watching another - a simple task for any PVR but not for a TV, unless it has dual Freeview tuners. I've had a PVR in the past that actually allowed you to record two channels while watching a third.
If the TV is a genuine Freesat one. Series link is built in to the freesat epg. However most TV's only have a single tuner. Some allow one tuner to make 2 recordings at the same time from a single transponder. eg Simultaneous recordings from BBC1-HD and BBC-2-HD are possible. An example is a single tuner Humax HB-1000S can do this.
It has to be plugged directly into the TV, and it gets formatted in a file system no other kit can read. Do not think you can unplug the drive and watch the files on anything else. There is however lots of kit that can record to a standard file system and use the recordings elsewhere.