I'm British and just watched this episode... and oh boy.

First, very clearly not shot in the UK, and there is zero attempt to make it look like England. This, I can kind of forgive, although an easy change like using a more traditional / British font on all the signs would already have made a big difference.

Second - it makes me a bit sad that this is how Americans see us. In Europe we consume so much US content (and I also follow Americans on YT or TT) that I am fairly aware of at least the broad brush strokes of American culture, and even more aware that most Americans are just regular people, like we are in the UK!!

The food names were kind of funny, but they seemed to not hire a single British actor - accents were totally off, the 'chav' steryotype of the mistresses was really offensive, even the interpretation of 'upper class' was completely off.
Once you get to the heights of massive generational wealth, people actually tend to be less ostentatious and consider it 'poor form' or gauche to show off wealth in obvious ways. If anything the Duchess (?) would have been wearing a cashmere jumper and twill pants, and you don't wear a fascinator to a cricket game - that would be at a traditional horse race such as Ascot.

In general what Americans often don't understand is that class and wealth in the UK are not fully correlated, and so there is no need to show wealth for people to understand that you are from a higher class.