Ah sorry for getting confused!
I understand the problem now - and to be honest I am not sure of the answer! In the DVD2 manual it talks about selecting EXT2 for recording purposes by highlighting TUNER, and then using the up/down arrows to highlight EXT 1, EXT 2 or CAM. I am not sure if this would would for playback?
However, let's go back to the start. If what you are actually trying to achieve is to be able to record from the DVB-C then I think that will work even with the DVD2 and DVB-C connected to different SCARTs on the back of the TV, and no connection between them. This is because SCART is two-way, hence when you ask the TV to record if will pass the DVB signal to the DVD2.
If necessary I will get my DVD2 out and have a play!