I agree with Mike. Scotland is beautiful. And I love Edinburgh. The train rides through the Scottish highlands would make Glasgow a BIG disappointment. But if you do go to Glasgow I'd recommend taking a train from there to Oban for some delicious scenery. I saw a rainbow over Loch Lomond when I went. So pretty. The train from Inverness to Kyle of Localsh was absolutely surreal. Kind of Legend of Zelda sort of feeling.
When it comes to the UK, north is where it's at. I went as far north as Culrain in October. A great place to visit if you want to get away from EVERYTHING including food, people, and traffic. Night time was absolutely deafeningly silent. Spent a week in a hot castle and had a paranormal experience every night. Spoooooky.
I'm going to get myself further north someday.