Optional 12.5% added to the bill
12.5%Sticks'n'Sushi's own site states an optional 12.5% service charge is added to the bill, and its terms say any discretionary charge is shown before you pay and can be changed or removed on request.
Source: Sticks'n'Sushi's own published policy. Service charges in the UK are discretionary: you can always ask for one to be removed.