pre filled fields

Dont really know how to describe but in my dashboard that offers free advertising there is a “add listing ” option , in one of the fields where the user can add their location is prefilled its editable for them but i need to edit it to a uk address instead of the address thats in there. the developer says it cannot be edited but i know it can be found somewhere but where ? i tried all files and cannot see it any help would be great thanks guys

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