Hi Viv,
Using the
Paris RER/Metro route planner I get the following:
Take the
RER B from CDG to Paris till Chatelet Les Halles station.
Transfer to the
RER A direction St Germain en Laye/Cergy/Poissy (any of the three will work) till Auber station.
Transfer to Metro Line 9 direction Pont de Sevres until Billancourt station. This is the closest station to Ave General Leclerc.
Remember that your
RER B ticket, a Billet Ile-de-France, is good for your entire trip, up until you leave Billancourt Metro station.
Use
Google Street View to get a better idea of your arrival station and how to walk to your final destination.
Best Regards,
Ben