I stopped at Zest and asked what was the best gluten free vegan option. The server told me they could make the jacket potato with mediterranean vegetables and feta vegan by substituting a tomato sauce for the feta. The portion size was very big and I enjoyed the meal quite a bit. The tea was only 84p as I ordered the special of the day. Their bakery case included gluten free vegan shortbread but I didn't try it as it looked a bit small for the price.
I wish Zest did have vegan cheese as they claimed to have but they were in the process of finding a new supplier. Apparently people did not like sheese, the old brand offered. I recommended Daiya but apparently it hasn't made it to Scotland yet.
Zest was extremely full at 1 pm and I ended up sharing my table with a very nice St. Andrews student. The service was very prompt though the girl I sat with had her drink delivered to someone else on accident.
I would go back to Zest again for a quick lunch in St. Andrews as my meal cost less than five pounds, including tea, and was hot and tasty.