Anyone who has a Series 2 Roadster will understand that Sleeping Policemen are a clear and present danger. The Plus 8 has almost "normal" ground clearance, in comparison.
My approach depnds on the type.
For the "pillow" type, which has a clear section at curb and centre I do as others suggest, place the car so that the centre gap is utilised, and then drive over slowly.
For the "table" type which in Wiltshire are a car length long a slow approach is all that is needed.
For the "Bump" type, which are mostly 30 to 40cm wide and 8 cm high a very slow speed is vital, 5mph or so.
Be very happy you are not driving in India: every roundabout on the main roads has a series of what they call "speed brakers" before the junction. They are more like "neck brakers"...
Bumps 
