I need to make up boundaries for a Google Maps mash-up.
I am trying to find boundary data for London - north, east, west and central.
Searching for hours I only found data for boroughs or postcodes.
Whats the best way of merging postcode boundaries into one polygon?
That way I can take all the London N, NW postcodes and merge them as a London North Polygon, then do the same for East West, South and Central.
Are there any tools (free if possible) where I can do this?
EDIT
This was marked as a duplicate question, but there is not an answer marked correct - just one answer that is a bit ambiguous about how exactly to merge the polygons using dictionaries & graphs and does not really make sense to me.