REDUCED SPEED IS PARAMOUNT WHEN DEALING WITH DOUBLE MINI ROUNDABOUTS
The best and only advice with these is to ensure you treat them as individual Roundabouts.
That is to say, plan your approach and exit point for the first Roundabout, this will put you in a good position by the time you come to exit in the approach stage for the second Roundabout.
It would not matter how many Roundabouts were joined together as long as you treat each one as an individual roundabout the same system works for each one.
Not very often you may come across a roundabout that looks like this one, and to be honest it runs very smoothly when dealt with in the correct manner.