Not sure what code I used in previous years, as it's just stored in the sat nav as "Clandon Show"
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However, I think either GU4 7RQ, or GU4 7AA should get you there. Looking at Google Earth, 7AA takes you to Epsom Road and, if you're travelling east, the turning for the show is a couple of hundred yards further up the road on the left (straight over the roundabout). Conversely, if you're travelling west on the Epsom Road it's on the right just before the roundabout at 7AA.
Here's a screen shot which may help:
Hope this helps,
Cliff