I assume you are talking about a legitimate as opposed to illegal set-up.
You will lose the Sky channels.
The satellite will get you the free-to-air overseas channels, eg, BBC channels, ITV channels, Channel 4, Channel 5, plus various more obscure channels. You don't have the subscription sports channels options.
If you want to get the Irish channels you will need a complementary Saorview set-up.
You need to decide whether you want a facility to record programmes and a 7-day EPG guide. This is similar to the Sky EPG but it is not the same and some people say it is not as slick.
You can get combos to include some or all of these options, eg,
https://freesat.ie/products/freesat-hd-recorder-saorview-package.
I don't avail of this service so this is not a recommendation or otherwise. I like my Sky
.