From where you are, it will be a little far to get around to a mosque, there are two mosques which take some time to get there but I guess you can spare the time for just once a week?
Ok firstly Tooting Mosque
Take the 44/270 bus down Garratt Lane to Tooting Broadway, when you get off at Tooting broadway at the end of Garratt Lane turn left onto Upper Tooting Road and walk down until you see a big white building on your right side:
Falcon Road Mosque:
Take the 44 towards victoria (opposite direction to tooting) and ask the driver to let you off at the top of Falcon Road, walk down Falcon road and you will see the mosque on your left hand side, I don't have a picture sadly :D you might see me there lol