My thai gf wants to come to the uk for a holiday but she will land in dublin which is not part of the uk in Northern Ireland.is there any issues for transit up to Belfast from dublin airport?

Not sure if anyone here is in a similar situation

Just wondering if anyone here can advise me please , I'm irish living in the uk.

My thai wife is living here with me on pre settled status .we want to travel to the Republic of Ireland for a family wedding and we are unsure of visa requirements as I think after brexit it has changed and a visa is required.

Any help with this would be great thanks .