Denise, a few years ago, Pat and I toured Ireland with OU and loved it. The Tour Director, Gerry O'Brien, was absolutely wonderful, the driver very good, the bus modern and commodious, with plenty of room as there were only (I think) 19 of us in a vehicle that could easily hold 35 if not more. OU limit their tours to not more than 24 guests, and the hotels in Ireland, with one exception, were teriffic. That one - not bad but just not up to the standard of the others - was changed the following year, by the way. The castle we stayed at the last night of the tour was really spectatular, and the meal that evening was a multi-course masterpiece. It certainly helped that the members of the group were all nice and friendly.
One thing we really liked about OU is that you only move every second or third day, mostly, and there were some very good "included' meals as well as some "on your own", with excellent suggestions from Gerry and, when near his home, from the driver as well (sorry I can't recall his name).
We've also toured with A&K and Tauck, both of which are more luxurious than OU, but in Tauck's case, only just slightly more. Most all of our travel is cruising; the great majority of that on Regent through Ngaire and B&K, but if we were going on a tour and OU had one that fit, they would be our first choice, unquestionably. Their big weakness, IMHO, is they don't offer tours in the US or Canada, where we're doing some travelling now.
We're on ORCA (Navigator to Alaska) now, with troublesome internet connections, but if you have specific questions, just post them here and I'll try and respond.
Enjoy Odysseys Unlimited! I’m sure you will.