Honestly, I don't even really care about seeing London a whole lot. The only reason I'm going at all is to see some friends. Perhaps I can convince them to just meet me in Kingston. If I do end up in the city proper however, I'll take your advice and hop on transit.
Everything else is duly noted. Any small-town suggestions like Lavenham are much welcome! Those are primarily the kinds of places I'd like to see,so thanks.
Perhaps I'll just make Isle of Man a 1-day thing. I have to get back to England anyhow, so maybe I'll just hang out on the island long enough to say that I was there and relax for a bit.
And yes, a lot of friends are telling me that I'm better off sticking to the coast of Ireland. That said, I might change my routing to go up to Galway as well so I can get a little more of it.