have it off/away with somebody

have it away (with someone)

To engage in sexual intercourse (with someone). Primarily heard in UK. I wouldn't have it away with someone you work with—it will only make things really complicated at the office. I can hear my neighbors having it away at night—it's really embarrassing!
See also: away, have

have it ˈoff/aˈway with somebody

(British English, slang) have sex with somebody
See also: away, have, off, somebody