Why do I think adding places to the site will make it less usable? Compare
Central London to
Greater London. Greater London is our worst sinner with 142 "Postal Towns" (a bad name for our London listings, but just to give it the name used elsewhere in the site) I find that page completely unusable personally, whereas Central London has 35 currently, far more manageable chunks. So in our worst case scenario, Central London suddenly multiplies from 35 Postal Towns to 300+ Postal Towns.
Also lets imagine RogerB works in a pub ;) he tells his friend it is in Westminster, but some helpful soul has known better and put it in St James Park, his friend successfully find Westminster in the list of places in Central London but can't find the pub. Admittedly arguably that problem is already there, but I think it is less of a problem than the proposed open it up completely approach.
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