Update on progress:
Car was been with the dealer for the past two weeks. The oil leak was a result of an aluminium washer failing on the gearbox drain plug; a new Copper washer has now been fitted and I am assured by the dealer that this has fixed the problem.
So I can now confirm that
there is a washer on the flush fitting allen key head drainplug on the MT75 gearbox.
Car came back to me an hour or so ago in dreadful rain...well and truly soaked.
I will monitor the situation but hopefully this is the end of the matter.
My sincere thanks to all those who offered advice via this forum.
