Religious weddings will require you to marry at an official location (church etc) while a Civil Registrar will only marry you at an approved location.
Secular ceremonies such as humanist and spiritual tend to have a bit more freedom, but the main thing to keep in mind is that you will need to do it in a public place, with a postal address. Your Solemniser / Planner or friendly Photographer will help you if you have any questions!
In Northern Ireland it’s slightly more relaxed in that you can be legally married anywhere you want, but restrictions will naturally apply for religious and civil marriages.
Of course if you are simply holding your own non-legally binding commitment ceremony you may hold this anywhere you please!
For all legally binding marriages you will need the appropriate documentation in order - the requirements for Ireland and Northern Ireland differ slightly so make sure you have checked through the appropriate website carefully.