Depends. On a weekend I'll go out and visit nearby areas or towns, so I'll spend bus/train fare + Starbucks (essential) + entry fee for whatever I happen to visit.
During the week, I'm not really spending much at all. I shop for groceries nearly every day (to see what's new in the Reduced section) and usually buy something, either a snack or something to cook for dinner. Other than that, I usually walk around on foot (except in London, where I spent £10 every 2/3 days topping up my transport card) and therefore save a lot of money. I also cook my own meals most of the time, so I further save money.
So I wouldn't be able to tell you...probably about a couple quid a day altogether RIGHT NOW (maybe £5/10 on the weekends) and maybe around £5 during my stay in London (including transportation fares).
Holy shit Lou, where do you spend all that money?!