Booking, calendar + payment system for a personal storage company

We require a software solution to encompass booking, calendar + payment system for a personal storage company aimed at students. Example Consumer Process: User will choose the size of storage required The required duration is then selected Collection address and date/time is designated Then the same for delivery address A ID and password is created Payment is taken The user interface will need to be simple, clean + concise. Specific capabilities Needs to be scalable over multiple sites + increasing no.s of users Bookings must be fluid/changeable + accessible by users Payment needs to be taken on site Price needs to be visible and change throughout the service selection process Only one or two user options per page Facility to charge people exceeding estimated store time Addresses should auto fill from postcode Estimated No. of users initially 100 - 500. Potentially up to 5000 No. of Admin 1 or 2