Mal, I had exactly the same on my previous '04 Roadster, the bonus is these are proper brass & copper construction as per Sospan's description & repair well
I'm pretty sure my OE drain plug boss as only soft lead soldered & there was a pinhole in this joint
One thing to note is not to use modern OAT longlife anti-freeze (contains organic acids) as these are known to attack some mixed metal rads containing soft lead solder
