@RoryAlsop @BobCross So, further investigation of the coolant leak shows that it's dripping from a small pipe next to the oil filter. I'm guessing that's an oil pipe, so it must be leaking from somewhere further up and running down to there.
Only thing that I would generally do is get the system nice and hot / pressurized, park it and creep around under the hood listening for a hiss and sniffing for coolant.
@NickC you don't have a picture do you - just so I can figure out where... what is above it? Are there hoses? Or is it from the engine block - which would pretty much mean gasket