Next summer my sister and I are planning to visit these 3 countries. We want to spend about 3 weeks there. So far our itenarary looks like this:

London- 4 or 5 days
Edinburgh- 2 or 3 days
Glasgow – 1 or 2 days
Dublin- 3 days
Cork City- 2 days

We will be travelling by rail or bus, since neither of us likes to drive. We also would like to visit a few more places in these countries that would be accessible by rail or bus. Any suggestions? We have heard a lot about the natural beauty in Ireland and Scotland and we would like to see it. Also we will be passing through Wales to take the ferry to Ireland and would like to know if we should stay there for a few days.
Any suggestions will be greatly appreciated!!