Thanks TMation. Just got back, I was away from home when I posted.
Sorry, should have waited until I got back.
Just been out to the garage, found my Haynes manual and indeed you are right, it would appear to be the oil cooler. The fluid is definitely coolant rather than oil. It seems to be collecting and dripping from the front underside of the oil cooler, so I'm guessing , as you say, it's either leaking from:
1. the oil cooler end of the hose from the lower right of the radiator (though no signs of moisture there) OR
2 from the front or the body of the oil cooler itself
I'll need to get the ramp out next week when I'm off and get some light on it. I can but hope that it might be a loose clamp on the hose or maybe even the hose itself. Failing that, a new oil cooler I guess?
Don't much fancy trying to get the exhaust headers off though "for best access" as prescribed by Haynes.
Hopefully though, if they say for "best access", that means it's "possible" to remove / replace it WITHOUT having to remove the headers?
Might also take the opportunity to remove the AIS and check the valve clearances as well, as I've got to drain the rad down anyway. We'll see.
Thanks again for your assistance.