As a currently studying student, some software providers offer you a student software licence at discounted rate. You can purchase the software from any high street or online retailer that participates in the scheme.
Please note that you will have to sign up for a Google Apps account (which you can do by clicking on the link at the bottom of this page should you need to) and this will give you an academic email address which can be used for purchases in most cases.
Below are a few links to various online stores that provide educational software:
Software4Students - http://www.software4students.co.uk/
SoftwareForStudents - http://www.softwareforstudents.co.uk/
TheUltimateSteal - http://www.theultimatesteal.co.uk/
Microsoft Dreamspark - https://www.dreamspark.com/Default.aspx
Note: You must re-register annually if you wish to use Dreamspark and you must have an OU Google Apps account
Studentexpressware - http://www.studentexpressware.co.uk/
Studentsuperstore - http://www.studentsuperstore.com/
Education-store - http://www.entec.co.uk/
Entec - http://www.entec.co.uk/
For Mac software discounts you will need to request a letter from Student Registration Services at firstname.lastname@example.org, confirming that you are a currently studying student and take that into a Mac store.
Student Apple store - http://store.apple.com/uk/browse/home/education_routing