I used Irondonkey tours to do a 6 day tour of Ireland. I did a self supported ride, which means they handed me a map and said see ya in 6 days! BUT, they have fully supported tours as well... the guy who runs it, Tony, was just awesome. This is very well set up and you stay in bed and breakfast the whole trip. Every AM you leave your luggage at the front door and when you show up at the next B&B it's there waiting for you!

The landscape is rolling with no true climbs. Rides were 35-50 miles per day. One of the best things to me was the fact that they have such loooooong daylight hours. So if you felt like sleeping in, or hanging out til noon, you could. Sunset was around 11pm! Also gave me plenty of time to stop and tour any neat sights, such as Kylemore Abbey and Ballynadich Castle. I used a rental bike, which was much heavier than my bike, but I was in no rush so it didn't matter! And much easier than dragging my bike thru Europe the rest of the time...

you can look at their tours here:

http://irondonkey.com/