As far as I’m aware of, the Freesat receivers/PVRs that comes with an Ethernet port either don’t have this port enabled or is provided for later use, e.g. a future TV-on-demand service. It’s not for accessing its hard drive remotely unfortunately.
However, there are several free-to-air PVR receivers available which provide HDD access via Ethernet/USB or even can record directly to a USB drive. For example the Technomate TM-6800HD receiver (some info here) will record directly to an external USB hard disk, which can then be connected to a PC to watch the recordings from. It’s recordings are stored as .TS files, much like those stored by most PC satellite tuner software.
You can pick up all the Freesat channels on a free-to-air receiver, however, you’ll not be able to access the EPG (TV listings) apart from the now/next info on a non-Freesat receiver. Due to the way ITV HD is broadcast, this channel needs to be manually tuned.