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I think you might have to elaborate on what exactly you are ultimately trying to achieve. Having read your post a couple of times i am still uncertain as to what you want.
Send Sky HD to 4 other boxes in HD would mean that you would have to do it via HDMI or over Cat 5e.
To enable you to change the channels whilst you are in either of the rooms, your options are the Sky+ app (not ideal also in my view) or via an IR link attached to each TV via a coax link from a set amplifier with IR/loft box with the use of the RF2 output on the box enabling you to do this. It goes without saying that you will only be able to watch the same channel in each room.