The representation of cartoon ballsack can be quite diverse. It might be used for shock value, humor, or to make a specific statement. However, it often depends on the creator's intent and the style of the cartoon.
One option is to check out local markets or flea markets. Sometimes there are comic shop stalls there. Another way is to follow comic book enthusiast forums or social media groups related to comics in the UK. People there often share info about good comic shops.