The tabloids still seem to like Fahrenheit for heatwaves, and I've heard it used reasonably often in summer - in offices etc. I can only remember hearing someone use deg F when it's 70+. It's certainly declining and not as common as say 30 years ago, but it's definitely one of the holdouts.

No one ever adds C or F, or even degrees very often, unless writing. It's -5; it's 30; it's 92, which are all self defining in UK climate.