My whole family uses Siri—both through our phones and through the HomePod mini in the kitchen—to add items to the shopping list.
Siri occasionally misunderstands the name of the item, or needs to ask who's speaking (when on the HomePod), or has trouble because the phone of the person asking has briefly dropped off the Wifi, but in the ~5 years we've had it, I can count on one hand the number of times adding has just failed with any pattern remotely like what you describe.
As a Brit, let me tell you, there is no such thing as a British accent. Our accents vary wildly by region, and sometimes those regions can be under ten miles away, let alone the huge differences between the four home nations. My own is basically what Americans imagine an English accent to be, a bit Hugh Grant but not as posh. Siri can do the basics for me, but playing some random song when any of us have asked it to do something completely different has become a running joke in our house. It's great when the kids try to set a timer or something and it suddenly starts blaring out some very sweary hip hop.
For me it's 80% accurate (including sometimes I'm entirely surprised it heard above all the screaming and howling) and then 20% it's just hilariously horribly wrong.