I imagine it all depends on the meat and cereal content of the sausage. Same with sausages from the butchers. You can buy ordinary ones that have a lot of cereal bulk, and some with 97% meat content. The difference in carbs is the difference in the cereal content. This is why the carb content will vary wherever you look. Maybe the chippy owner could tell you?
What I do with a chippy tea is have a fish and some mushy peas. I scrape all the batter off the fish and add a little vinegar. I actually enjoy this a lot more than I used to when I ate the batter. The peas may or may not play havoc with his levels, but they are OK for me as long as I don't overdo the quantity, and they are full of fibre. I have made sure the chippy we use doesn't sell sugar-added peas.