Oh Streatham's fine, it's actually perfectly pleasant, especially at the Streatham Hill end. (For OP's benefit Streatham suffered a bit in the 80s and 90s, then started to smarten up and became a good place to buy if the budget wouldn't stretch to Brixton, Balham or Clapham... as such it's had a dose of the up-and-comings in recent years.) But it's not especially fancy more a practical, sound and sensible place to live.