@Bushmillsbabe
You don't have to answer these, but here's a few markers:
Do you say Red Sauce or Ketchup?
Napkin or Serviette?
Toilet or loo?
When you didn't hear, do you say pardon, sorry or something else? What about if you burp?
Do you care which piece of cutlery gets used for what in a meal?
How do you thank people?
Is it a lounge, living room or sitting room and does it contain a sofa or settee?
What is your evening meal called and what is the final course called?
Is your progenatrix mother, mummy, ma, or mum (and how often do you drop obscure latin terms into what you say?)
That's just a few linguistic markers. There are also loads connected with taste in decor, furniture, books, music, cultural entertainment, how milestones are celebrated etc etc. And whilst many people will ernestly protest that none of these matter, people still clock them and notice if someone is using options on any of these that they don't expect.