I've done it occasionally in UK restaurants where the service clearly did not meet the level expected for the overall charge. It's certainly not a regular occur

I've done it occasionally in UK restaurants where the service clearly did not meet the level expected for the overall charge. It's certainly not a regular occurrence but equally it doesn't keep me up at night (it's optional, we don't have a warped view of tipping here and I wouldn't dream of withholding it unless the experience was undeniably poor)