most common seems to be hbv as said. Other options are, stat housing, oil cooler cover plate and coolent bridge in the v of the engine, due to the the slight back angle of the engine etc most leaks run back over the bell housing and down off the 2 bolts under the gear box.
Then their is core plugs to cylinder head, seen a pic on here of coolent deposits around the dis pac area on right hand drive cars. I beleive left hand drive cars have the wiper mechanism reversed, so presume the scuttle drain and dis pac may well be on the other side as well. Which may make it easier for hbv to spray water to the left side (as you sit in it)of the engine bay. Maybe..?
If its core plugs, if a bottle of bars stop leak potion dont fix it(1 only per system or you risk blockage) then its head off time. Rare but also consider external head gaskit leak. Water pump too but as that at the front of the engine presume not relevant here.
Hth.