At about 8:30PM I went to my village's convenience store of a well-known UK chain. I go there a LOT, have done for years, and have never had a problem.
Background: I currently have an evil cold of doom, so I can barely smell anything.
When I got into the store, I was overwhelmed in the entrance by the extremely strong smell of some kind of air freshener. That was pretty odd, considering my cold, and it was like the shop has been drowned in the stuff.
I walked to the back of the store (tiny store, so not far at all) and it smelt like... Feces, rotting and death. I kid you not. I have never smelt anything so foul (and my cat recently had diarrhea). It filled the entire back and middle of the store. I had to hold my breath to get my shopping done.
I saw the manager, who I know by name and said, "[So-and-so], there is a horrible smell back there!" and she just... Laughed.
Whilst the cashier abandoned her post and spray more air freshener all over the store, which made absolutely zero difference.
My God it was gross.
On the topic of service, just a little slow and irritating. I put my stuff down and the cashier just stared at me for a minute before actually scanning the items. Then when I went to pay by card, she just stood there.. And stood there... And then asked, "Any cash back?" Uhm, no. Then there were no bags so she tried to shove the receipt at me whilst I was desperately trying to balance everything in my arms.
Annoying, but nothing worth crying over or complaining about.