Well i live in a flat and it’s a communal Ariel so i can’t get to it. But i don’t see how i could get it before but can’t get it now. You may of just answered that guffer but if you did i don’t understand the technical talk
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If it's communial then there should be a splitter for each line. I forget the exact technicalities but you have to be careful of the V and H sync (I spent ages dealing with this when I lived in Germany) as you cant get a splitter to deal with both at the same time. I think you need a splitter on each feed and then take a feed from each one but maybe someone with more nouse can better advise.
Again if Sky installed this then they should have done a better job 
Each LNB channel can operate in 2 frequency bands and in horizontal or vertical polarisation. Your set top box sends signals up to the LNB to select a combination of band and polarisation depending on the channel you are viewing / recording.
Two channels may be on different combinations of the above so you need 2 feeds to view/record 2 channels and that has always been the case although if the channels selected are on the same multiplex it's possible that the box may be able to record them using a single feed.
In a communal system you will normally have a quad LNB generating feeds for each of the possible combinations, and a system that splits and switches the appropriate LNB output to each resident's box. You will still need 2 feeds from such a system to get full Sky plus functionality though. Something to pester your landlord about, I guess. :-/
There are devices that can distribute 2 feeds down one piece of coax but you'd need to install a splitter / combiner both at the distribution system and behind your set top box.
Kevin