checking for bad postcodes

You may have noted a spate of bad code reports north of Brighton from me last evening.  As a new postcode mapper of - oh, about 3 minutes - I've been checking the data by using the postcode map at free the postcode:

http://dev.openstreetmap.org/~random/postcodes/

This uses the npe codes as well as free the postcode codes to produce a postcode map at, for exapmle, BN1 level.  Bad codes show as unlikely or even crazy post code zones on the map.  For example, islands of BN1 in BN5 zones and even of SP1 in BN.  These seem to be bad postcodes on the NPEmap and I've reported them.  

Probably a well known method but useful.  let me know if there is anything I can do.

Best wishes
Mark