A 60-year-old woman with type 2 diabetes, managed with Metformin 1g BD and Gliclazide 80mg BD, presents for her annual review. Her HbA1c is 68 mmol/mol (target <53 mmol/mol). Her BMI is 32 kg/m$^2$, and her eGFR is >60 mL/min/1.73m$^2$. She has no history of cardiovascular disease. According to NICE guidelines, what is the most appropriate addition to her current medication?