post codes not shown

I'm used to sorting Tomtom v3's , not done much with the Nav 3 Tomtom Start models.

I didn't realise the post codes were integrated and the "post code" section in fast activate was greyed out which lead me to believe I had made an error.
When I (more carefully) viewed "navigate to" menu on my Start 25 there is no "post code" menu just "address" and then I input post code under "City/Code" .
The TIPKG file does not allow (I think ) viewing so, for a relative newbie with the Nav 3's, I was unaware the post codes were integrated and there is no separate Post Code section in the device navigation menu.

Many thanks, as always for your kind response and availability to assist.