well, a good way to budget your spending is to plan where you want and the activities that you plan to do in the 3 weeks there... i usually put them in an excel sheet so it's easier to compute... put the dates on the left side.. then the estimated cost of a certain activity we plan to do for that day... then print it and have it as my guide...
you can also settle for a certain amount of spending money per day.. e.g. £100 per day and if you go over that, at least you would know...
