You say that its on the left side as you look under the bonnet but that you can only see the drip under the engine. Does this mean that you see the drip looking down into the engine or just the dripping underneath?
I imagine as you haven't been able to identify roughly where the drip is you are just seeing it under the engine on the left hand side. This being the case, is the undertray still fitted? If so the water could be dripping anywhere and just running off the tray on the left side.
So I'd say that unfortunately you need to do a bit more looking.
If the leak is on the left side, that is indeed where the water pump is. The pump is external to the engine block driven by the fan/aux/drive belt (on the left of the engine) - its bolted to the block low down and also bolted to the power steering pump - so they turn as a (sort of) single unit.
The pump draws coolant through a hose from the oil cooler. However, if the drip is running along the undertray, there are a myriad of other hoses that may be leaking. These could be to do with the expansion bottle, cabin heater, IRD cooler or EGR cooler. If the cabin heater were leaking, that would be visible inside the cabin, not the engine bay. I think all the other items would drip onto the undertray. Given the age of the cars, it could also presumably be a corroded core plug - it looks like there's 8 on the L Series.
So I think you need to identify a bit more closely where the leak is originating from. Sometimes this can be very difficult, however, it sounds like you have quite a serious leak so that may actually help you!