I want to set my novel mainly in inner city London. I do not know the areas intimately and wonder whether I would be better to invent an inner city district, rather than use real places but get the geography slightly wrong? Any views?
If you named any fictional inner city London district in a convincingly British way, I would never doubt its credibility. But that's just because I don't know anything about London. On the helpful side, a fictional section of London would be much easier to write; you just take the details needed (dirt, homeless people, double decker buses, etc.) and basically fit it together for your needs. Examples could include certain companies or clubs that are central to the story that don't exist in the real world. I for one have no problem with made-up locales in real-world settings. If I were writing it, it would probably be easier to make up this London district instead of researching one.
It depends what time period your book is written. Is it contemporary or historic? If it's historic, Victorian London had some grungey parts of town -- particularly SOHO. Contemporary Soho went from slummy to artsy to expensive. Sort of like Haigt/Ashbury in San Francisco -- it was a hippie place and now its full of white rich people playing at being hippies.
It may not be the answer you are looking for but research is the key. It's not just a question of geography but the character, the feeling, the smells, the people.... the list goes on. Geography is the least of your worries. Google Maps can take you there geograpically but for the rest you really to visit in person. It does depend on whether or not the location is central to your story and only you can answer that. If the location does not intrude too deeply you might be able to wing it. Again, you would be in the best position to judge. Sorry I cannot be of more help.
google maps (street view) is your best friend. visit some parts of london, if on looks like what you need there you go.
