Hi,
Think about your interests/skills/expertise in other subjects: which A levels did you do? If you did physics, for example and enjoyed it/did well, you could select a topic related to that e.g. perhaps a program to run a school practical on current/voltage or diodes/resistors that works out various parameters from entry of raw data OR if you are into mechanics/cars, perhaps a system to calculate, using matrices, the forces encountered by a certain automobile component then coming up with design data using these.
My background is in biology/medicine and when I did an MSc in CS, my project was to create a software package to record, store, analyse and retrieve patient information in a particular branch of medicine. The main languages taught in our course were java and sql, so I used a mysql database to which I connected my java GUI with JDBC.
Do you know some sql - if so you could create something in similar lines, but in the context of your background.
Hope this helps.
M