Obviously, there were lots of cool places on the London/Edinburgh/Dublin trip, but when it comes to cool gift shops there is a clear winner: the gift shop at the Churchill War Rooms.
We are not very gift-shoppy people, but we left there with some cool WWII reproduction prints to hang on the walls. And a "Make do and mend" keychain. But I have a bit of a WWII-homefront obsession, so there were also tons of things I very nearly bought (including some quite tempting reprints of WWII home-front-related books such as ration cookbooks and a guide for English war brides headed to the U.S.). The war rooms themselves are pretty cool too. [edited to say: Upon reading through this, I realize I used the word "cool" WAY too many times in those few sentences. But what's done is done, and I'm letting them stand, but with apologies.]
Other shopping highlights: Chocolate bars from Rococo Chocolates. (The woman working at the counter was the nicest shopkeeper ever and gave us samples. We went to the one in Belgravia.) Yarn from a knitting boutique in Edinburgh. Though it is difficult for a novice like me to figure out what to make with one skein of yarn picked at random with no plan in mind. Hmmm.
And the all-important food category: Of course, the area isn't really known for having great food. And some of our experiences definitely confirmed that (we had maybe the worst Italian food ever at some place near Westminster Abbey, and the smell of heavy unpleasant bar food hung thick in the air of Edinburgh). But we also ate a few meals I'd be more than happy to repeat.
So, if you're ever in the area, here are some recs. We ate a very yummy lunch at Mildred's, a vegetarian restaurant in Soho. And we had a tasty dinner at Henderson's Bistro, a vegetarian restaurant in Edinburgh (though I cannot recommend the cherry pie). Another really good dinner in Edinburgh was had at Ristorante Gennaro, an Italian place. And I also really loved Wagamama, a chain of noodle places. We visited Wagamama toward the end of our trip when I wasn't feeling too great and the Moyashi Soba was just what I needed, like chicken noodle soup for vegetarians, only better. Upon returning home, I had a dream that a Wagamama was opening up in the Chicago area and the level of excitement actually woke me up.