Why are you drinking more water when a study just proved drinking 3-4 cups of tea a day is better for your body than water. you get all the hydration, plus antioxidants and it's good for your teeth. I don't feel like finding the link for you but ya, you're british, keep with the tea.
If you want to work on your push ups try the 100 push up challenge. It's really neat.
http://hundredpushups.com/
and then just try going for a run in the morning, or the evening to get your stamina up for those god aweful shuttle runs.