So Sytner have told me, as per all you other guys, that this is a characteristic of the engine. They are claiming the noise is from the engine and is nowhere near the gearbox, it explains why you can still hear it in Neutral or Park. The master tech drove me in their 67 plate demo car which whined, but not as loudly.... but this was a low mileage car at 2800mls, mine is a high miler at 5600mls, so it's acceptable for it to be audible of everything else by 5600mls. Even this guy was commenting m about how terrible they sound.
Personally I think this is going to cost them a fortune in the future, I'm suddenly reminded of the N47 timing chain issue, which was again a "characteristic", and not in anyway shape or form a design flaw. God knows what that noise is if it's internal to the engine, but it cannot be good.
Basically if you buy a x40i B58 engined car, be preprared to pay a lot of money for a car that sounds like it's broken. You will not be able to do anything about it as it's a characteristic. Bad luck if you bought the car before it started making the noise, it's acceptable for a £37k (list price) car to sound broken after 5600mls. Any other manufacturer would just fix this, BMW as per their MO will do anything to avoid paying out.
My exhaust flap is also rattling and BMW are saying they don't have a fix, and won't give a MPE free of charge. So I have rejected the car on the grounds of the exhaust rattle as that is a genuine fault and not a characteristic. Looking forward to getting my deposit back and getting out of the car, lucky escape. To say I'm bitter about this is an understatement. I do not like being treated like an idiot, nor do I like have my purchase experience utterly ruined. I will never, ever buy another BMW ever again. If they don't look after their more "expensive" customers god knows what it must be like in a 114i.
So for Google purposes, if you are looking for problems, whines or common faults for your buyers guide for your BMW 140i, 240i, 340i, 440i then here's the lowdown: your car will sound like it has a nakered differential, or gearbox, and this is normal. I will make it even more simple for you: BUY SOMETHING ELSE.