There are a few threads on here about this... my 2013 model didn't accept the full postcode until I updated the maps and software recently. You'll need a software version equal or greater than 2.21 if my memory serves me correctly. There was a CD to update the software included with the maps. I don't know if a software update alone would be enough to get the full postcodes working as I didn't try one without the other, unfortunately!
To check your software version, press the "Setup" for 5 seconds, select "Radio telephone diagnosis", then "Unit description". The software version is at the bottom of the next screen. Mine is RNEG2.85.A.5 for example.
Thanks for the link, i have just updated mine now as it had ver2.7, i was having intermittent boot problems in normal use so hopefully this will fix that now, this new 2.8 version does offer postcode entry as long as you insert the postcode in the town sectionEdited by: freestyler71