Oil pressure switch location

Hi all I'm trying to locate the oil pressure switch on my 2006 Astra 1.8 coupe I bought it as a run around back and for to work its got bit of a oil leak on sump seal but other than that car seems ok.reason for change of pressure switch is when car is idle the oil light comes on and as soon as I drive car oil light goes out the car is well in the safe level with oil on dipstick but been told be a friend to change the oil pressure switch any ideas would be very grateful for help

Many thanks...

Oil pressure switch location