Well my mini's sat around for a few weeks while I maintained a gut feeling that the primary gear is causing the whine. The after talking to a mini expert and then reading in the 'Mini Expert' magazine about how a worn primary gear will cause a road car to whine I think my gut feeling is now justified so I orderered and replaced the primary gear.
Yesterday I was putting it all back together when I snapped one of the three bolts that hold the clutch spring cover to the pressure plate

I searched my manuals but couldn't find a torque setting so I guessed 20lbs, seemed too easy so thought 30lbs should do it... snap! So now another set back, fortunately I have a spare pressure plate and I'm waiting for the arrival of another bolt that 'MiNi MuLiShA' has kindly offered to send me.
So hopefully by the weekend I'll know whether it was the primary gear, if it still whines there will be a FREE mini available at the bottom of a steep cliff!
Stay tuned