And not just for the coffee!!
Having sadly stopped their Seville Orange free from cake and a different chocolate brownie which was wheat and dairy free, they have introduced a dairy (and wheat) and gluten free Chocolate and Hazelnut Loaf cake. Although out on display in most stores they will sell you a sealed and wrapped one if you wish to be especially careful.
AND they have some meal boxes which are free from allergens too!
Costa have only ever offered a few gluten free food choices, and Nero's used to offer wrapped carrot and raisin cake bars which were Wheat, Dairy and soya free but stopped them recently. Full marks to Starbucks for great coffee AND free from options!