You can save a bundle by ditching Sky, but you'll lose the movies and foootie.
You'll get BBC, ITV, C4 etc from a FTA system.
An aerial will be needed for RTE etc. It's the same aerial whether it's DTT or analogue. So, you can't lose on that.
For the better quality of DTT (albeit not guaranteed available) you should expect to pay 50-100 euro for an external MPEG4 decoder unless your TV has one built in. I've seen one for 150, I think that's too much when you consider the UK ones cost from 50 up.
UK DTT (aka FreeView) decoders do not work here unless you're on the border & then only for UK channels.
Do bear in mind that even if you get a MPEG4 DTT tuner now, it could be rendered worthless if the new system were to use an incompatible encryption technology....so son't spend more than you can afford to lose on a decoder.