Centre Prop & Oil Seal
 

Not exactly the news I was hoping for...

Car has been in for a full service, and they have found:

1) Centre Prop bearing is worn - causing an annoying whirring noise in the cabin

2) Suspected oil leak from the rear engine seal - engine out job to fix

Damm!

Ouch. As someone also facing a big bill for repairs, I feel your pain and wish you the best of luck fixing it.

What's caused the rear oil seal to fail?

Usually caused by either wear (high mileage) or overfilling the sump with too much oil which puts a lot of extra pressure on the seal causing it to fail

Mine seems to be doing this. How did you diagnose?
I can't tell where the noise is coming from as when I turn my head.
It sounds like some metal being gently turned on a lathe or almost like a hosepipe running but not as loud.
I will try jacking up and spinning the wheels today and hope it is not a prop bearing.