- Ordanance Survey - https://www.ordnancesurvey.co.uk/business-and-government/products/os-open-names.html
- Dr Fry - http://www.hannahfry.co.uk/blog/2012/02/01/converting-british-national-grid-to-latitude-and-longitude-ii
Install the Postcode app, and create a postcodes.db as follows
This bit assumes you are running some variant of Linux. You may need to adapt it if you are using Windows or Mac OSX.
You will first need to fetch the data. Go to https://www.ordnancesurvey.co.uk/opendatadownload/products.html and scroll down to OS Open Names and make sure "Supply format" is CSV. Then Shift+Select all the items in the list from HP to TV to get all the data.
You will get an email after filling the form out. Copy the contents of the email into a file list in this folder and fetch all the links into a folder by doing something like this:
mkdir Src
cd Src
cat ../list | sed 's/http/\nhttp/g' | grep "http" | grep "zip" | while read u; do wget "$u"; done
You will now have a folder Src full of zip files with awkward filenames. Extract them like so:
for f in *; do unzip -u "$f"; done
cd ..
And this will dump a DATA folder into the Src folder, while taking you back up a level to this folder.
To process this into a useful database, just run the following:
./mkdb.py Src/DATA
And once it has finished, you will have a postcodes.db :) Put this into /sdcard/postcodes.db and the offline backend should pick it up.
This can then be used by the Postcode app to read off your postcode without an internet connection.