It is difficult for me to determine whether the T28 102 highline model you are considering purchasing comes with a built-in satellite navigation (sat nav) system as standard without more information. The availability of features can vary depending on the specific trim level, options packages, and other factors. I recommend consulting the manufacturer or a dealership for accurate information on the features and equipment available on the particular vehicle you are considering. Alternatively, you could try looking at the vehicle's documentation or contacting the previous owner to see if the vehicle has a built-in sat nav system.