Well,
I was out with the car at the weekend and there were no leaks with the engine running. It didn't leak all day and there were no drips visible between sessions. Clearly the scavenge side of the pump is emptying the valley in the sump very effectively!
It only leaked when left overnight.
I think I have discovered what has been causing the sump to leak.
The brass threaded fitting with the strainer is screwed into a steel "cut in half nut" that has been bronze welded into the valley of the sump.
Because it is a nut and not a machined fitting, it is not flat on the face that butts up against the dowety washer.
The original nut that has been used as a fitting, has a beveled "lead in" on the thread. No doubt very handy on its original purpose as a nut.
The oil is seeping out around the threads and escaping out around the metal part of the dowety washer. None of the rubber seal is in contact with the face of the "Nut" due to the bevel.
The face of the nut is also covered in small dents and burrs where no doubt the nut has rattled around in the stores before it was cut down to make the threaded part of the oil strainer fitting.
So, I have very carefully drained out the sump pan and completely cleaned off all of the oil from the threaded part involved.
Once I was completely sure that the metal parts were chemically clean and dry, I have carefully coated the threads with "Loctite 542" and reassembled the fittings.
I guess time will tell how successful this option will prove to be!
Wish me luck!
