The new postcodes zip file is also posted in here, no idea if it will work on your original Go - does the full postcode search work at the moment ? You might need to upgrade your Go's software - you can do this on the Tomtom site - get Tomtom home - instructions are on there aswell.
What ever you try make sure you have got a full back up first.
The new map & keygen should work for you though.
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