I have never had much success with SatNav postcodes but have figured out how to overcome this...
Google the caravan site's postcode then zoom in the map and inspect the surrounding area in satellite view until you find the site. This will often be some distance from the postcode.
Zoom in further until you can see the actual entrance to the site. Right click upon that entrance and select "What's here?" from the menu that appears.
In the Google search bar, you will now have the precise co-ordinates for the site's entrance, which can then be input directly into many SatNav devices.
As long as you do this correctly, you should never get lost again.
Satellite navigation, like most technology is excellent when used in combination with common sense. Unfortunately technology is used as a substitute for common sense all too often.
I used mine again yesterday and went miles out of my way down a single track country lane. I then discovered that my wife, unbeknown to me is dyslexic! She'd put the post code in as she read it from a piece of paper. She read it out to me the same way as she had put it in, with the last two letters reversed! I'll know better next time!
------------- Some days you are the dog,
some days you are the tree.
In the dark distant past when I was at sea we had a term 'Radar induced accident' where an office took more notice of a Radar and incorrectly interpreted the information leading to an accident - all instead of eyesight, charts and common sense. I think we now have the same issue with Sat Navs in cars. 30+ years on and little changes.
------------- 'A sure cure for sea-sickness is to sit under a tree'