There was a post a few pages back about blocking tailgaters on a dual carriageway - that’s just outright dangerous at that speed. Pull in to the inside lane and let them on their way.
I think the only time I intentionally piss off a tailgater is if I’m on a 20 or 30, someone’s needlessly sitting at my arse and I’m about to take a left turn off the road. Sometimes I’ll gently slow down way more than I actually need to to make the turn, like a geriatric would. It’s quite funny when you see them absolutely beeling behind you.