If the sandwiches are "lovely" then i doubt they're using low-fat mayo

. So i would point that at 3. 1 point for sweetcorn if that's involved too

and the butter/marg again probably not the lower fat variety and a bit more generous than the scrapings we allow ourselves! So I would point at least 2 for the butter.
Which is why I turned down a tuna/sweetcorn may baguette in a cafe yesterday! Though sadly went for the tuna may baked potato before i realised baked potatoes were more points than the boiled version. Doh!