For months and months my oil light used to flash when ignition on and when it was warm no matter how I was driving it used to buzz and flash. So today I thought IDE have a real go at it. After replacing the oil pressure switch then driving it for 30 mins no change, then thought if its a pressure issue maybe there's a leak somewhere, but no. Then a lightbulb moment and I remembered my dipstick has always been quite loose, so I put some ptfe tape on my dipstick to tighten it in the hole and walla, after idling for 30 seconds I turned it off and left it 30 mins. Then I went out, ignition on and no oil light flashing, drove it around town between Leeds and Bradford, both motorway and town driving for about a hour and a half upto temperature, no problem or light or buzz whatsoever. Really chuffed now and wanted to share my findings with people as I know it's quite a common problem. Could be a cheap and easy fix for you