Ain't is quite common here.
/etymological_hat
originally a contraction of am not, and in proper use with that sense until it began to be used as a generic contraction for are not, is not, etc., in early 19th cebtury. Cockney dialect of London; popularized by representations of this in Dickens, etc., which led to the word being banished from correct English.
It's actually a proper English word from about the 18th century.
Although, because of our melting pot, it's commonly replaced with ", innit?"