As an American, the word "ass" is used to refer to buttocks instead of "arse." However, there doesn't seem to be the same sexual context in the British word. So, I was wondering if there was a British equivalent to the idiom "piece of ass" (For non-Americans unfamiliar with the phrase, "piece of ass" is basically a vulgar, slang, idiom used to describe a women in an objectifying manner in which the person uttering the phrase considers her to be a suitable sexual partner. For example, you might tap your friend on the shoulder as a beautiful woman walks by and say, "Look at that piece of ass. Wouldn't mind spending a few hours in
that.").
The motivation for this thread is is that it is usually preferable when writing fantasy to use as much British English as you can, and American idioms showing up in the text can sometimes be jarring. I need some dialogue for gruff, uncouth troglodytes hanging out in pubs, but American vulgarities may not work. So, if any of our generous non-Americans are feeling charitable (or Americans who are familiar with British idioms), please tell me any British idioms which carry the same connotation as "piece of ass." Especially if they include a vulgar word for a body part.
Thanks to the blessed souls willing to help.