If you have UFC Fight Pass, you are eligible to watch UFC 252 Preliminary Fights. To open the access to the main event, you will need to buy the PPV from the UFC.tv. All you need to do is just hitting the order button in the UFC.tv. Choose the UFC 252 PPV package. Keep in mind that you could also choose to watch the bout a month later when it is added to your Fight Pass library.
Ireland viewers can tune in the Eleven Sports. As mentioned, BT Sport will no longer provide the service starting from December 3rd. You will want to purchase the PPV through the UFC.tv for a safer and more comfortable option. If you already have the UFC FIGHT PASS, the process will be much easier. Not to mention that you can also watch Preliminary Fights live stream for free by using your FIGHT PASS credentials.