Hi Candice,
Do you plan to finish your trip in Ireland, or return to England? If you are planning to finish your trip in Ireland, be sure to check if the car can be returned in Ireland.
When booking your rental car, be sure to inform the rental company of your itinerary and confirm that the rental agreement allows for cross-border travel between England, Scotland, Northern Ireland (Belfast), and the Republic of Ireland. Some rental companies may have restrictions or additional fees for taking the car across international borders. Typically passport, driving license, and IDL is more than sufficient but be sure to double-check with the hire company.
Be sure to check out this page on
Driving in Ireland which has some key information.
If you have any other questions, be sure to let me know.
Cathaoir