I tried (and failed

It gave me the option of going to OX2_6[blank, blank] but OX26_[blank, blank, blank] didn't seem to exist.

I thought I could omit the postcode and just use the town and street name to find my destination...
I knew the town name, and street name which I entered into the guidance setup (the system recognised both), but then it went back to the postcode prompt automatically before I could start the guidance

I was unable to figure out how to start the guidance without entering a postcode

Do I just need to find an up-to-date sat-nav disc with a current database of postcodes, so it recognises OX26_[blank, blank, blank] or is this down to 'user error'???