I'm planning a trip and looking for recommendations

[kilted2000]

I'm planning on going to Ireland and Scotland in late July - early September, where should I go and what should I do? I have been to Scotland before, 20 years ago, but I didn't really see much except the highlands as I drove through them. I am also going to England and Wales if anyone has any recommendations there as well. I lived in England for a year so I know it relatively well. I will be getting around mainly by train and bus. I love history, have a degree in it, but I also would like to see a bit of the country as it is now as well as in the past.