I'm currently working around the area trying to get all the local places cross referenced properly. I've got The 2012 Index of Places from the ONS which has a supposedly complete set of places, but I've been hitting a number of problems which I think I've finally sussed.
The OSM wiki defines 'hamlet' as less than 100-200 people, but village supposedly starts at 1000 up to 10000 with the proviso that it depends on the country. Ideally the two would perhaps meet :) We are perhaps looking at a population of around 8000 for a town designation in the UK, but anything down to 100 is still classified as a village by the ONS. What are actually missing from the OSN data are ANY hamlets despite their claiming to include them.
My first exercise was to add links on the OSM data to the wikipedia entry for each village, and there is a small list of miss matches which I'm trying to sort out. However when cross referencing the population data reported by wikipedia quoting the 2011 census, but what that fails to account for is that only provides totals for the whole parish, which may have more than one hamlet/village. The IOP data contains the 'BUA' population for the villages, but omits the rest of the hamlets that make up the parish/ward.
The IOP data is released under the Open Government Licence V2 so I see no problem using it in OSM or Wikipedia? I think what we are still looking for is a consistent list of hamlets to work from to fill in the gaps? The IOP data was supposed to be updated annually, but it seems only annual updates are currently being generated.
To add to the fun, the six digit codes I've been using for LLPG data for many years have been replaced by a 9 digit code. While the 6 digit code had a nice three level structure, the 9 digit code has lost the third layer, but these still only go down to the ward/parish level. There is still no ID for the town/village :(
And Scotland and Northern Ireland are separate data sets ...