If you're connecting more than one satellite receiver to a dish you'll need a dual (or quad) LNB attached to the dish. (If you've currently only got a single LNB fitted you can buy a dual one for under a tenner). You'll then need a separate cable from each LNB output to each of the two satellite receivers.
As I wrote before, a generic satellite receiver (which is what a Sky + box is without a subscription), attached to a dish pointing at the group of satellites used by Sky, can receive all of these channels:
https://en.wikipedia.org/wiki/List_of_free-to-air_channels_at_28%C2%B0E
They include all Freesat channels (and many more) but Freesat and Freeview are two different companies, with different channel availability. Freesat has more channels than Freeview but there are a few Freeview channels (such as Dave) which aren't available on Freesat.