A follow up on this. Chillly (http://www.openstreetmap.org/user/chillly) has
rendered tiles with the postcodes on which you can use in JOSM and other
editors. Currently he's loaded Birmingham for us but plans to do the other
areas too. Follow the instructions here to use it:
Hi all,
Thought this may be of interest to some of you (obviously I don't mean for
adding to OSM!), if you haven't already seen it...
http://wikileaks.org/wiki/UK_government_database_of_all_1%2C841%2C177_post_codes_together_with_precise_geographic_coordinates_and_other_information%2C_8_Jul_2009
