You would be surprised how many tent hire companies there are in Ireland. Due to how hard the island has been hit by Mr Recession more and more people are choosing tent hire over traditional brick and mortar event locations to save a bit of money.
You may be surprised to learn that due to the amount of variety on offer, you should be able to find a tent hire for half the price of a conference hall and yet have a tent that offers all required comfort and atmosphere. And since we are in Ireland, yes one of those categories is indeed how to handle the weather.
You can now hire tents in Ireland in all shapes and sizes. White is generally the best choice as it suits pretty much all occasions and it allows heat in and out pretty freely so if its a very hot day your guests wont be sweating. However if you want a fancy purple tent or any other colour, you should be able to find it very easily. As far as the shape, you can get peaked squares or you can get tents that are designed to look just like houses together with little windows. The variety is endless and the main advice that I would give you is to try to see the type you choose in person. It's very difficult to judge how a tent feels from the inside by looking at a photo.
There is simply one rule here and that is too big is better than too small. Therefore the only limitation on the size should be your wallet and your venue. No guests are ever going to leave a party complaining that the tent was too big; however an event where every one is on top of each other probably won't be a lot of fun. A lot of people suggest that eight to ten feet for each person is about right and I would agree with this. Don't make the surprisingly common mistake however of not counting in the caterers and the additional space required for dancing etc.
Here you essentially have three options, fully enclosed, partially enclosed or open. Because we are in Ireland and Ireland always seems to have terrible weather whenever you want there to be nice weather, you may be tempted to go with fully enclosed. A fully enclosed tent will have walls that keep out the weather. Nowadays such tents can withstand quite a lot of wind and rain so this is a very good option if you're nervous about the weather. I would generally avoid open tents as if it rains your event will essentially be ruined and chances are it will. If you do think that there is a reasonable chance of a sunny day, a partially enclosed tent will offer a bit of protection from rain but will also allow you to enjoy the sunshine. Basically, it's a bit of a gamble and therefore I always advise at least hiring a partially enclosed tent.