The Golf's playing up. Must be because I've polished it.
When the oil's warmed up to 80 odd or so, the oil pressure lamp comes on if the engine's allowed to idle. Rev it at all, and it goes back off. I've previously had the buzzer come on a couple of times during normal driving, (ie, above a couple of thousand revs, oil not stinking hot and not cornering like a loon) but it's always gone off after a second. Oil level is fine.
Pointers on whether this sounds like oil pump, dodgy electronics or the bottom end of the engine dying would be nice.