Just checked the car as outlined above.
Mechanical noise is a whirr not a rattle.
Increasing engine revs increases the frequency of the whirr until at about 2.5k revs it is just a high pitched whine - less audible as a noise though because it has been overtaken by the noise of the engine.
The gear oil was changed by the dealer during a service carried out on behalf of the last owner in April 15 - though the invoice just says: LGEAROIL Gear Oil Qty 5 (I assume litres). I will now see if the dealer can advise me on what oil was used. The car has covered 2k miles since the service.
