For OP's sake and any others reading along, I hope people carry on putting Streatham down, @minipie. Keeps it good value for her!
I suspect it's what I diplomatically called a proper London mix. Everywhere I lived in London was like this (except Fulham, briefly). Now most areas are smoother, glossier and, umm, whiter. Fewer traditional Turkish/Syrian/Greek grocers, more artisanal delis. Not so much chicken & kebab shop, more seventeen varieties of milky cha and a marinated tofu panini. Less nappy hair and dreads than blue hair and caramel highlights (not on the same head, one hopes).
Several of my favourite 'upscaled' London pubs have closed in the past year. They were nice, having solicitously retained their establishments' heritage while refitting the interiors (reclaimed furnishings, natch) as restaurants with vastly improved food at eye-watering prices geared towards the Young Professional. Those YPs seem to be feeling the pinch now, they're probably doing Gordon Ramsay impressions in their over-fitted kitchens. The pubs should've actually retained the heritage, given it a coat of paint and varied the menu a bit.
I confess that I felt very ambivalent about being part of the 'gentrification' of Clapham, Wandsworth, Brixton, Tooting and Colliers Wood. And I didn't like them as much when that process was complete - it isn't in Tooting, yet, and Brixton's still a weirdly mixed bag. Streatham's much better value than any of them, having wedged its limited-edition trainers in a pothole and refused to budge!
Last time I looked at Colliers Wood, it was still in the liminal space between upscaled and not. But Streatham's houses are bigger, and it has good schools.