I believe ISS (Image Supply Systems) used to do limited equipment rental (Canon and Bronica) at one time – not sure if they still do. You’d have to give them a call to find out
Conns in Dublin do ( http://www.connscameras.ie/ ) you can rent out L lenses and high end cameras even tripods and so on for a day/weekend or week. If you then decide to buy they knock the highest rental charge of the retail price. They can be on the expensive side though. If you do buy a camera from them they do sensor cleaning on it for free. You might want to make sure that they price match on the best retail price in town before deciding to rent /buy from them – that way you will definitely come out ahead.