Our only other stop in UK besides London was Bath. I have wanted to go here for SUCH a long time. As a Jane Austen fan, I was definitely wildly curious about this high society hang out. This little city was absolutely darling! We arrived by a beautiful scenic train route (took 2 hours), and stayed for two nights before heading back to London to fly to Barcelona.
We booked our accommodation on AirBnb, and it had to be one of the most comfortable bnbs that I have ever stayed in. Only a 2 minute walk from every attraction, beautiful interior and gorgeous typical bath building. It was also so well equipped. We were met by our host that showed us around and had even stocked the fridge for our breakfast the next day (how lovely!). Would recommend this AirBnb in a heartbeat. Only a 5 minute walk from the station also. You can take a look at the listing here.
Top attractions to see are the Roman Baths and the Abbey. We didn't encounter any lines at either, but we went early morning or late afternoon. The baths are actually open quite late.
The Baths were super interesting, there is a lot of history there. You can get an audio guide at the entrance to learn about it. You can even try the water when you leave. Paolo and I gave it a go - it tastes awful just so you know!!
Also, the Royal Crescent and The Circus. Both so iconic, and gorgeous to see the rows of terrace houses. We took a walk from the centre of town. Bath is the kind of city that you walk everywhere.
We also did a half-day tour to Stonehenge. It was only an hour hour, and going with a tour we had all our tickets ready to go and could enter immediately. The tour gave you 2 hours to explore Stonehenge - which was 1.5 hours too long in my opinion. It was brilliant to see, but once you see it that's it right! I think you only need 2 hours if you choose to listen to the audio guide from absolute start to finish.
We weren't really overwhelmed with food options. Only one place of note: Sally Lunn's Buns. And we were lucky enough to be staying just outside it! These are so wonderful, you definitely have to go up to the cafe to try, and then take some away with you for later.
I didn't do any shopping in Bath. But there are the usual shops - H&M, Urban Outfitters etc. There are also a few speciality boutiques scattered about selling handcrafted items. It's lovely to look through.