I travel solo all the time, and found
ABD a *FABULOUS* way to travel on your own. I totally understand the reasons you list for traveling alone, and I've always been in favor of going alone rather than not going at all!
ABD *will* charge you a "single supplement", which is an extra approximately 30% of the trip price. It's not a bad percentage as singe supplements go.
The guides are great, and very helpful, and if you tell them you're traveling solo & nervous about it, they'll "keep an eye out" for you. Everyone I traveled with on my tour was very friendly, and I never felt "alone" unless I wanted to be. If you're going to travel alone, a tour like this is the best, safest way to go, especially to a foreign country.
As far as the Ireland adventure goes, I know there are some Trip reports on this board if you search for them.
Sayhello