Nav question / Frustration

I've been in Whitby for a week with the A3 (I'll write it up later), but I have a question about the Nav that has infuriated me:

We were trying to get from Whitby to Station road in Cayton - This was a random choice so I didn't have the chance to research it properly before we set off (I don't trust any Nav that far), I put it in as we were driving and it directed me quite happily. Fortunately, it was somewhere I'd been before so when I was diverted in a direction, I was suspicious as I knew it was wrong. It seemed to direct me to the nearest station road (in Scalby as it turned out).

I reset it to direct me to Cayton (the centre of) and set off again - While en route, I changed it to Station Road, Cayton and it immediately directed me to the nearest Station Road, this time in Scarborough. I gave up and decided to try putting in the Postcode....

I wanted to get to YO11 3TL (Playdale farm park) so put in YO, but there was no option for inputting the number (that I could see) so scrolled through the 500 YO postcodes starting at YO1 onwards. It stopped at YO10 and I could search no more.

At this point, my 2 kids were going nuts in the back and we went to Peasholme park in Scarborough instead.

So - am I doing something wrong and can someone try this with their Nav to see if both circumstances are user error?

Thanks

JTW :)