Hi shana, i know about warehousing large amounts of cacao beans, the basic principles should apply for small scale too.
humidity will cause mold if you don't keep the air moving, you need a well ventilated place. if the air is dry then ventilation is less important. so for instance if they're in a closed cupboard in a humid place, and particularly if they're very dry, like below 7%, they will uptake water and can get moldy. you could leave the cupboard door a little open and put a small 15cm fan in there and it should help the problem.
temp is not as important, generally speaking the cooler the better so 15-18 is no problem at all. when you get up into tropical temps you have to think more about it.
you want to keep the beans away from potential contaminants and odors as they can uptake those too. so if there's dust, if you're cooking strong odors nearby like garlic, if the cabinets themselves have any kind of food or chemical odor, or if they're exposed to smoke of any kind, you can have off flavors in the beans and hence the chocolate. also this is more for when you have a concrete floor/walls, but they should be off the floor on wood pallets and never touching the walls. I cover the floor and walls in heavy gauge plastic to avoid contact and/or contamination.
finally there are some bugs that will attack cacao beans in tropical climates. i can't imagine its a problem in ireland but if you have ventilation holes or leave the cupboard door open, you may want to screen the beans off with a simple flexible mosquito mesh to stop small moths or flying baddies from getting in there and laying eggs in your beans.
hope this helps,
brian