Freesat, not Freeview. Freeview is only available through a TV aerial, Freesat is only available through a satellite dish, the two are not the same (this is also why you can't get Five, it is available on Freeview, not on Freesat).
To be able to watch the Sky subscription channels from the Sky box downstairs, you need to run an RF cable (aerial lead) from the RF2 output on the back of the downstairs Sky box into the aerial socket on your upstairs TV - and tune your upstairs TV to whichever channel the downstairs Sky box is outputting on. This will allow you to watch whatever the downstairs Sky box is showing upstairs, by tuning your TV to programme number 6.
You will still be able to watch your non-subscription Sky box upstairs by connecting this via scart to your upstairs TV.
The Magic Eye bit is where this might become tricky - a Magic Eye allows you to change channel on a Sky box from a remote location. So, in theory you could press the buttons on a Sky remote in your bedroom and change the channels of the Sky box downstairs. This is all well and good when you do want to change the channels of the Sky box downstairs, but isn't so good if all you want to do is switch from one Freesat channel on your Sky box upstairs to another Freesat channel - because you will end up changing the channel of the box downstairs as well. I would stick with the RF connection to your TV from the downstairs box, but don't go down the Magic Eye route as you will end up falling out with whoever is watching the subscription Sky box downstairs very quickly.