If going to free satellite route you will get the ITV's, BBC's, C4's, FILM4, etc etc but NOT RTE/TV3/TG4 - you will need to get an aerial for these unless you go for a combo box satellite and digital terrestrial receiver which receives the sat channels and the RTE digital channels (assuming you are in an area where RTE is currently broadcasting the test digital channels)
Tony from www.satellite.ie gets good recommendations over on boards.ie (no connection with me, not even a previous customer)
but as I said, with a combo box it really is quite simple to receive all the channels if you are in an RTE digital area. Think most of Dublin is anyway.