on 15-10-2020 09:19
on 15-10-2020 09:24
If Northern Ireland you can use your phone as normal as it's part of the UK.
If ROI you can still use your tariff, but only for 63 days in any 4 month period as you will be roaming in EU, so the answer depends on where in Ireland to be accurate.
on 15-10-2020 09:38
15-10-2020 09:41 - edited 15-10-2020 09:42
15-10-2020 09:41 - edited 15-10-2020 09:42
You'd be bound by these T&C's with a UK contract https://www.o2.co.uk/help/pay-monthly/roaming-in-europe
So if you are moving permanently, I'd wait to get a contract there.