Fitness First Marylebone in City of London | Facilities,... Fitness First Marylebone is a gym in City of London, offering gym and fitness facilities, strength and cardio training, membership enquiries. Address: Cavendish Mews N, London W1W 6XAOfficial website Things to do today Things to do tomorrow This weekend Free events Family events Kids activities in London Live music in London Live sports in London Cinemas in London Gyms in London All London events