Short answer: RESOLUTION

Stuff Fibre (with my persistent prodding) finally, after 45 days of bickering, got a Senior Chorus management to admit that - despite their adamant "testing" showing that provisioning and line speed were all perfect - all along their provisioning had been at fault.

Post provisioning correction - download about 95+Mbs - in line with what I would expect from my old 100Mbs max ethernet on board chip.

Upload still strangely around 50mbs (expecting 20max), but who am I to argue?

Moral: if your service quacks like a pig, its not the butterfly they are selling you.  And being pig headed helps.

Thank you for all who helped with advice and comments.