zackster it’s the same over there. You’re even getting your sarcasm all wrong. It’s a chip butty - both singular. Chips butties? Just say it.
Here’s a quiz for you, Zack:
In the US do you eat:
A. A cheese and onion sandwich?
B. A cheese and onions sandwich?
C. A cheeses and onions sandwich?
D. A cheeses and onions sandwiches?
And please remember, at all times, we invented the language. It’s English for a reason.