I'm in the USA using antenna and cable services. We don't have satellite service in our household. In North America cable and satellite service is similar in that subscribers use a cable converter box or satellite receiver for tuning those services.
With my cable converter boxes the most common connection from the converter box to my Panasonic recorders is the composite (RCA) yellow video and white and red audio. Another connection I use from the converter box to my Panasonic recorders is S-Video and (RCA) white and red audio. You might have SCART outputs and inputs on your Sky Digibox and Panasonic DMR-EH57. (North America does not use SCART connectivity.)
Your Sky Digibox is an "external tuner." There should be outputs on the Sky Digibox that may be connected to similar inputs on your Panasonic DMR-EH57.
Once the Sky Digibox output is connected to a Panasonic input you would use the Panasonic recorder remote to select that input as the recording source. You should be able to record whatever channel is tuned by the Sky Digibox.
Once the Panasonic recorder is connected to your TV you will use the TV remote to select the input where the Panasonic recorder is connected.