There have been many students that have faced this problem that use card payment or contactless quite often than cash. 
The cafeteria accepts payments by card if we spend a minimum of £4 which is expensive if you would want to just get some snack or a drink or even a meal deal and not a proper course meal.
I personally have ended up buying more things that I do not realy need just to reach the limit for card payments.
The nearest ATM being at the Train station, it causes inconvenience if you do not plan on spending on campus but in an emergency you have to. 
Thus an ATM in the campus would be helpful for the students , as it is in Townhill Campus.