Advice needed - help!

OK so I'm finally thinking of taking the plunge and moving to London. If I get the job I'm applying for I'd be working in the Denmark Hill area. I'll be looking for somewhere to live in South London. Any advice on decent areas in South London that aren't off the scale expensive (I could afford up to about 700/month for a one bed place) and not more than about an hour's commute from Denmark Hill? I know this is a bit specific but I love London and know the centre quite well...but could never afford to live North of the river!!

Any tips or advice would be gratefully received. Thanks!!

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