I don't think it matters whether it is a case of £25 a week, or £200 a week. The money spent through your business is yours, and whatever you waste is coming straight out of your pocket. This isn't to say that it's your fault, usually there is way too much else going on to notice the odd loose pound rolling around the place.
How often have you said "O, it's only a couple of quid?"
An ex-colleague of mine once said, "Look after the pennies and the pounds will look after themselves." Every time I weigh up the cost of something, this phrase flashes through my mind and I think of a hunched up old woman (with a similar likeness to the wicked witch in Sleeping Beauty). But it does the job.
Have a think about the small expenditures that go through your business, things like:
Milk, tea and coffee
Couriers and sending recorded mail
Train, taxi and general travel spend
Simple but regular and accurate admin and a bit of expense and travel research could go a long way to save a lot of money.
Ask yourself, could you be spending the pennies more effectively?